Add symbols to unicode punctuation

[wooorm]

The current commonmark definition of “ASCII punctuation character” does not only include the unicode punctuation characters within the ASCII range, but also the unicode symbol characters within the ASCII range: $, +, <, =, >, ^, `, |, ~.

I think this makes sense. I think that users would not know the difference, and would indeed expect to be able to escape * the same as $.

I think it is also sensical to broaden the definition of unicode punctuation the same way, so that there’s no difference between $, £, and €.

Currently:

*$*a.

*£*a.

*€*a.

$a.

£a.

€a.

(EDIT: if GH supports this PR, the emphasis does not work in the above 3 cases, when it doesn’t, emphasis works for £ and € but not for $)

Proposed: none turn into <em>s (note this is not a useful example, I am sure it could be possible to come up with a better one).

Note, S (symbol) includes the subgroups:

gc ; Sc                               ; Currency_Symbol
gc ; Sk                               ; Modifier_Symbol
gc ; Sm                               ; Math_Symbol
gc ; So                               ; Other_Symbol

Note, all unicode characters, all unicode categories

[jgm]

I'm in favor of this change -- does anyone see a problem with it?

[rlidwka]

This needs an example in the spec, otherwise parsers that use spec as compliance tests might miss the change.

[wooorm]

added a test case!