PHP: Added CSS embedding to heredoc/nowdoc

[troizet]

Added CSS embedding to heredoc/nowdoc.
Partially implements feature request #5010.

Before:

After:

Based on discussion #7933, I was able to piece together the puzzle and add CSS embedding to heredoc and nowdoc.

The CssEmbeddingProvider and test code is borrowed from the Javascript2 VUE module.
The background highlighting code is borrowed from the HTML Editor module.

I also encountered a formatter execution order issue, which was described by @matthiasblaesing in commit be093c3. I solved this issue by adding a hack to TaskHandler.java:
https://github.com/troizet/netbeans/blob/f9f1f9fe22e4a46f4910a476449725c4a72fbb7f/ide/editor.indent/src/org/netbeans/modules/editor/indent/TaskHandler.java#L170-L186

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[tmysik]

I am afraid that I am not able to fully verify the editor-related implementations but overall, the change looks good to me, thank you.

[troizet]

@tmysik I've made the corrections.

[tmysik]

@troizet thanks!

[troizet]

Updated the pull request. Fixed the slowdown when opening PHP syntax highlighting settings.

[matthiasblaesing]

@troizet in general this looks very nice. I have a concern about scalability of the approach. I tripped over the modification to the lexer structure and the introduction of a special tokenid for CSS. Given that the referenced ticket already asks for HTML, SQL and JSON I see this growing in the future.

Please have a look at this illustration for the idea:

8cdb9af

The use of the property token allows us to transfer the info from the lexer to the analyser without changing the token ids. New mapping would just report a different mimetype. This is currently considered an implementation dependency so the property was marked appropriately and the constant defined outside the exported classes.

What do you think?

[troizet]

What do you think?

Great idea! I'll try to make some changes as soon as possible. Thanks!