add notice about missing screenshots in devtools

[connorjclark]

This is to address bugs in prod with Lighthouse, Performance Panel and Recorder Panel:

https://bugs.chromium.org/p/chromium/issues/detail?id=1483420 https://github.com/GoogleChrome/lighthouse/issues/15460#issuecomment-1775760096

I added a warning aside to the top of relevant pages. This will be resolved in a ~week, so it doesn't make sense to translate these. I didn't use the banner: system because that would require editing too many files' frontmatter - a URL check was significantly faster.

Small issue is the "project overview" page doesn't have CSS for aside stuff, and I don't know how to include it.

[chrome-devrel-infra[bot]]

:white_check_mark: Preview (static) for commit 3a2bff532d92814b7a645f2a8fda8ec3472924b2 available at https://pr-7642-static-dot-dcc-staging.uc.r.appspot.com/.