Context menu item to only appear when image is right-clicked

[domportera]

Is your feature request related to a problem? Please describe.

Right-clicking on non-image elements displays the Search By Image context menu entry

Describe the solution you'd like

Only show the context menu entry when an image is right-clicked

Describe alternatives you've considered

editing userchrome.css, but I've found no success

Additional context

A good place to test this feature is at this old website as it is html-only with no hidden background images

[dessant]

https://github.com/dessant/search-by-image/wiki/Why-is-the-extension-always-visible-in-the-context-menu%3F