chore: add permissions trivy-docker

[jsjoeio]

Looks like I didn't give this workflow the right permissions: https://github.com/coder/code-server/runs/5432361797?check_suite_focus=true

I am not sure if actions needs write permissions or if security needs write permissions so I added it to both.

Fixes N/A

[codecov]

Codecov Report

Merging #4957 (5b2b8cd) into main (643ef13) will not change coverage.
The diff coverage is n/a.

❗ Current head 5b2b8cd differs from pull request most recent head b6c3297. Consider uploading reports for the commit b6c3297 to get more accurate results

@@           Coverage Diff           @@
##             main    #4957   +/-   ##
=======================================
  Coverage   70.54%   70.54%           
=======================================
  Files          29       29           
  Lines        1677     1677           
  Branches      371      371           
=======================================
  Hits         1183     1183           
  Misses        420      420           
  Partials       74       74           

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[github-actions]

✨ Coder.com for PR #4957 deployed! It will be updated on every commit.

• Host: https://codercom-pbbq5g86g-codercom.vercel.app/docs/code-server
• Last deploy status: success
• Commit: b6c3297
• Workflow status: https://github.com/coder/code-server/actions/runs/1952847087