Update existing prometheus documentation to include configuration options for ServiceMonitor

[shaun-nx]

Proposed changes

This PR adds to our existing prometheus document to add steps on creating a ServiceMonitor resource.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[ADubhlaoich]

Changes LGTM!

[codecov]

Codecov Report

Merging #4414 (12c01f1) into main (abe4950) will decrease coverage by 0.03%.
The diff coverage is n/a.

❗ Current head 12c01f1 differs from pull request most recent head 90da571. Consider uploading reports for the commit 90da571 to get more accurate results

@@            Coverage Diff             @@
##             main    #4414      +/-   ##
==========================================
- Coverage   52.11%   52.08%   -0.03%     
==========================================
  Files          59       59              
  Lines       16956    16956              
==========================================
- Hits         8836     8832       -4     
- Misses       7823     7825       +2     
- Partials      297      299       +2     

see 1 file with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more