docs: Add contour trafficrouter plugin

[wilsonwu]

Checklist:

• Contour support #523 Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional with a list of types and scopes found here, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I've signed my commits with DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My builds are green. Try syncing with master if they are not.
• My organization is added to USERS.md. (in another PR chore: Update test and related docs for plugin name standard #2728)

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[github-actions]

Go Published Test Results

1 948 tests   1 948 ✔️  2m 34s ⏱️
   118 suites         0 💤
       1 files           0 ❌

Results for commit 8111b47.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (e7e45f7) 81.47% compared to head (8111b47) 81.47%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2729   +/-   ##
=======================================
  Coverage   81.47%   81.47%           
=======================================
  Files         133      133           
  Lines       20154    20154           
=======================================
  Hits        16421    16421           
  Misses       2881     2881           
  Partials      852      852           

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[github-actions]

E2E Tests Published Test Results

    4 files      4 suites   3h 27m 41s ⏱️
  96 tests   80 ✔️   5 💤 11 ❌
404 runs  365 ✔️ 20 💤 19 ❌

For more details on these failures, see this check.

Results for commit 8111b47.