feat: add Commonmark HighlightExtension

[kbond]

Twig/Symfony currently only allows registering extensions (not renderers) in the service container. But in general, I think packaging these two renderers into a single extension is useful.

[brendt]

Thanks! I've moved the README contents to https://tempest.stitcher.io/highlight/01-getting-started, so I'll add your section there as well!

[coveralls]

Pull Request Test Coverage Report for Build 8831279193

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 0 of 5 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 94.059%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/CommonMark/HighlightExtension.php	0	5	0.0%

Totals
Change from base Build 8831264520:	-0.3%
Covered Lines:	1425
Relevant Lines:	1515

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💛 - Coveralls

[brendt]

Tagged: https://github.com/tempestphp/highlight/releases/tag/2.3.0