Coveo z-index + make sticky

[lamATnginx]

Proposed changes

Closes https://github.com/nginxinc/docs-platform/issues/398 and https://github.com/nginxinc/docs-platform/issues/403 and https://github.com/nginxinc/docs-platform/issues/410

Before (z-index issue):

After (z-index issue):

Before (sticky):

After (sticky):

Checklist

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

• I have read the CONTRIBUTING document
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• I have updated any relevant documentation (README.md and CHANGELOG.md)

[nginx-jack]

z-index, sticky working great now 👍 .
There's a small issue with the searchbox change the sidebar position (which I think was masked by the breadcrumb having some initial height when they shared a row).
On a fast connection it's a flicker on page load, but on anything slow the sidebar very obviously shifts down when the searchbox loads.
Maybe a min-height on the div around the searchbox, that matches the known height of the searchbox? 🤔
At some point, would could implement a skeleton loading thing.. but that might be overkill!

[lamATnginx]

Thanks for the feedback. Addressing it soon.

[lamATnginx]

Ready for review again.

[nginx-jack]

LGTM - The search box still flashes on page change, but things aren't shifting around anymore.
I'll make another bug for the searchbox flashes.. we might need to pre-render that search box, before coveo loads in or something. For another ticket anyway :) .