Short answer: Periods are the default counter suffix for ordered list implementation in web browsers.

Long answer: If you are using ordered lists in web pages, browses are implementing them using period after. If not specified, the default value will be "\2E\20" (". ", a full stop followed by a space). You can check a specification example: https://html.spec.whatwg.org/multipage/grouping-content.html#attr-ol-type

The Arabic numerals is just a type from possible predefined counter styles the https://drafts.csswg.org/css-counter-styles-3/#predefined-counters. Because of typography and internationalisation demands, the W3C invented ways to overwrite the defaults.

The suffix for the counter can be changed from the default period to <string>, <image>, or <custom-ident>.

Also common I've seen parentheses (")", closed round bracket, called unpaired parenthesis). Depending on the hierarchy of your ordered lists you might need to go multiple levels down, so you might need multiple counter suffix styles (periods '.' for level 1, single parentheses ')' for level 2, paired parentheses '()' for level 3, colon ':' for level x, etc. ).

1.  
  1.1 ...
     (a) ...
2)  or (2) ...
3)  or (3) ...

Regarding your question about international convention. I don't know, but you can read more about the topic at https://writing.stackexchange.com/a/5685

Short answer: Periods are the default counter suffix for ordered list implementation in web browsers.

Long answer: If you are using ordered lists in web pages, browses are implementing them using period after. If not specified, the default value will be "\2E\20" (". ", a full stop followed by a space). You can check a specification example: https://html.spec.whatwg.org/multipage/grouping-content.html#attr-ol-type

The Arabic numerals is just a type from possible predefined counter styles the https://drafts.csswg.org/css-counter-styles-3/#predefined-counters. Because of typography and internationalisation demands, the W3C invented ways to overwrite the defaults.

The suffix for the counter can be changed from the default period to <string>, <image>, or <custom-ident>.

Also common I've seen parentheses (")", closed round bracket, called unpaired parenthesis). Depending on the hierarchy of your ordered lists you might need to go multiple levels down, so you might need multiple counter suffix styles (periods '.' for level 1, single parentheses ')' for level 2, paired parentheses '()' for level 3, colon ':' for level x, etc. ).

1.  
  1.1 ...
     (a) ...
       a.1: ...
2)  or (2) ...
3)  or (3) ...

Regarding your question about international convention. I don't know, but you can read more about the topic at https://writing.stackexchange.com/a/5685

From an usability point of view, I think a suffix is needed since it clearly states to the user that it is a list-item and not a value. For example, reading:

1. apples
2. oranges

I will know it's an enumeration and not a quantitative information:

1 apple
2 oranges

So whatever suffix you will be using (if it's an international convention or not) I would suggest to use a suffix in order to mark ordered lists accordingly.

Short answer: Periods are the default counter suffix for ordered list implementation in web browsers.

Long answer: If you are using ordered lists in web pages, browses are implementing them using period after. If not specified, the default value will be "\2E\20" (". ", a full stop followed by a space). You can check a specification example: https://html.spec.whatwg.org/multipage/grouping-content.html#attr-ol-type

The Arabic numerals is just a type from possible predefined counter styles the https://drafts.csswg.org/css-counter-styles-3/#predefined-counters. Because of typography and internationalisation demands, the W3C invented ways to overwrite the defaults.

The suffix for the counter can be changed from the default period to <string>, <image>, or <custom-ident>. Also common I've seen parentheses (")", closed round bracket, called unpaired parenthesis). Depending on the hierarchy of your ordered lists you might need to go multiple levels down, so you might need multiple counter suffix styles (periods for level 1, single parentheses for level 2, paired parentheses for level 3, etc. ).

1.  
  1.1 ...
     (a) ...
2)  or (2) ...
3)  or (3) ...

Regarding your question about international convention. I don't know, but you can read more about the topic at https://writing.stackexchange.com/a/5685

Short answer: Periods are the default counter suffix for ordered list implementation in web browsers.

Long answer: If you are using ordered lists in web pages, browses are implementing them using period after. If not specified, the default value will be "\2E\20" (". ", a full stop followed by a space). You can check a specification example: https://html.spec.whatwg.org/multipage/grouping-content.html#attr-ol-type

The Arabic numerals is just a type from possible predefined counter styles the https://drafts.csswg.org/css-counter-styles-3/#predefined-counters. Because of typography and internationalisation demands, the W3C invented ways to overwrite the defaults.

The suffix for the counter can be changed from the default period to <string>, <image>, or <custom-ident>. 

Also common I've seen parentheses (")", closed round bracket, called unpaired parenthesis). Depending on the hierarchy of your ordered lists you might need to go multiple levels down, so you might need multiple counter suffix styles (periods '.' for level 1, single parentheses ')' for level 2, paired parentheses '()' for level 3, colon ':' for level x, etc. ).

1.  
  1.1 ...
     (a) ...
2)  or (2) ...
3)  or (3) ...

Regarding your question about international convention. I don't know, but you can read more about the topic at https://writing.stackexchange.com/a/5685