docs: add proxying a vue app

[jsjoeio]

Special thanks to @abhinav1912 and @Blakeinstein for helping with this!

Fixes #3918

[github-actions]

✨ Coder.com for PR #4033 deployed! It will be updated on every commit.

• Host: https://codercom-9qq2slkpv-codercom.vercel.app/docs/code-server
• Last deploy status: success
• Commit: 8cf98ea
• Workflow status: https://github.com/cdr/code-server/actions/runs/1164443105

[codecov]

Codecov Report

Merging #4033 (8cf98ea) into main (d0ca3ae) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #4033   +/-   ##
=======================================
  Coverage   63.51%   63.51%           
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  Files          36       36           
  Lines        1872     1872           
  Branches      379      379           
=======================================
  Hits         1189     1189           
  Misses        580      580           
  Partials      103      103           

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[jawnsy]

whooooo vuejs

[jsjoeio]

@nekomeowww I totally forgot to tag you on this but I added a bit about proxying Vue apps to our docs

[nekomeowww]

@nekomeowww I totally forgot to tag you on this but I added a bit about proxying Vue apps to our docs

Nah, it's fine. It was happy to see you guys update those documentations quickly and actively.