[Feature] More obvious reporting of script syntax error

[BalaM314]

Motivation
When a sub-frame user script has a syntax error, the UI only shows the error after opening the extension menu, and then selecting "sub-frames only scripts". This is very easy to miss.

Proposed Solution
Display a ⚠ badge on the extension logo, or another easy to notice warning.

Use Cases
It would make it easier to debug syntax errors, as currently it is very easy to spend a few minutes looking through logs wondering why the script isn't running.

[tophf]

We can show the warning text or icon on "sub-frames only scripts" title.

The badge is limited to just a few characters. We can add ! to the badge but I'm not sure it'll be clear, so maybe we'll add a third color in the options (red by default) which will be used in this case.