Add Node.js to list of languages on README and demo languages

[pxpeterxu]

trafficstars

Motivation

Related to https://github.com/DMOJ/judge-server/pull/1143:

After enabling support in judge-server for a Node.js-based executor, we need add the language to the demo instance and the documentation

Changes

• Add JavaScript (Node.js) to the demo instance's languages list (language_all.json)
• Add Node.js to the list of supported languages in the README

Testing

Ran python3 manage.py loaddata language_all and verified the languages were loaded properly in the Admin interface

[pxpeterxu]

Thanks for the review @Xyene and sorry about the extreme lateness of this follow-up. I just made the requested changes, so this should probably be good to go.

I'm not sure who's the best to merge this in, but @kiritofeng and @quantum5, might either of you be open to taking a quick look? (I see you've made some of the most recent merges)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 47.72%. Comparing base (435839e) to head (9081526). Report is 83 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2297      +/-   ##
==========================================
+ Coverage   46.78%   47.72%   +0.94%     
==========================================
  Files         251      260       +9     
  Lines       13309    13745     +436     
==========================================
+ Hits         6226     6560     +334     
- Misses       7083     7185     +102     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

:rocket: New features to boost your workflow:

• :snowflake: Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• :package: JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.