feat(plugin-shiki): export bundled languages and their names and improve performance

[Mister-Hope]

1. isSpecialLang includes isPlainLang
2. loadedLanguages should be unchanged after highlighter is resolved.
3. User might need to get these bundledLanguages sometimes.

[coveralls]

Pull Request Test Coverage Report for Build 9280447759

Details

• 3 of 5 (60.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.01%) to 56.505%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
plugins/plugin-shiki/src/node/resolveHighlight.ts	3	5	60.0%

Totals
Change from base Build 9280370196:	-0.01%
Covered Lines:	996
Relevant Lines:	1576

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💛 - Coveralls