Add support for the comma-separated scope list synatx in sublime-syntax files

[anima-libera]

It is possible to define multiples scopes in a scope: field by separating them with commas like in

scope: meta.interface.xxx, entity.name.xxx, etc.xxx

however the syntax of sublime-syntax files doesn't really handle that correctly (only the first comma seems handled and the auto-completion breaks on the next capture for example).
This is not a big issue, but resolving it may add a + to the SS++++ ranking of this extremely good package ^^.

[keith-hall]

Are you sure the commas don't become part of the scope? (I'm not at a computer to check - the show_scope_name command on a token you've scoped with commas should reveal it... I guess if it did, it would be impossible to select them as comma is an operator in scope selectors. ) Typically scopes are stacked just with a space, no need for commas.

[anima-libera]

Oh, my bad, scopes are space-separated... I couldn't find this anywhere, I only found an answer on the Sublime Text forum that says that scopes are comma-separated. Commas on comma-separated lists of scopes do show up when using the show_scope_name command, but everything else seems to work fine just as if they where space-separated.
Sorry for this non-issue then.
But still: when using the comma-separated syntax in a sublime-syntax file, the first comma is given the scopes

source.yaml.sublime.syntax meta.block.contexts.sublime-syntax

and the second one is given the scopes

source.yaml.sublime.syntax meta.block.contexts.sublime-syntax string.unquoted.plain.out.yaml

as if commas were only partly supported (or maybe they have an other use that I am not aware of, since documentation on the sublime-syntax syntax is rare on the Internet ><).

[FichteFoll]

The first comma should definitely be part of a string scope, so I fixed that for the next release. However, commas and other special characters in scope names aren't really expected or supported. I haven't experimented with what characters are allowed, but you would certainly be unable to match a literal comma with a scope selector, since the comma is an operator there.