* Set code languages for various files (part 1)

* Revert LaTeX change for now

* Update files/en-us/web/api/performance_api/server_timing/index.md

Co-authored-by: Brian Thomas Smith <brian@smith.berlin>

* Update files/en-us/learn/javascript/building_blocks/conditionals/index.md

Co-authored-by: Joshua Chen <sidachen2003@gmail.com>

* Update files/en-us/learn/javascript/first_steps/variables/index.md

Co-authored-by: Joshua Chen <sidachen2003@gmail.com>

* Fix selected languages

* Fix selected languages

* Fix selected languages

* Apply suggestions from code review

Co-authored-by: Joshua Chen <sidachen2003@gmail.com>

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Co-authored-by: Brian Thomas Smith <brian@smith.berlin>
Co-authored-by: Joshua Chen <sidachen2003@gmail.com>