allow height to go to ~50px

Sometimes my notes are very short and I like to make it take less vertical real estate on the page. If you can do this, I am sure there will be many happier users. :)

The issue names no files or tests, so first locate the note panel's height or minimum-height styling in the Firefox extension and inspect how short notes are rendered. Verify manually with a very short note that the panel can shrink to approximately 50px without obscuring its contents.

Written by the indexing model from the issue text.