[FEATURE] Hide Activities button

[p-sage]

Is your feature request related to a problem? Please describe.
I think it would be nice to add an option to hide the "Activites" button (the button at the top left corner of the screen), the same way as we can hide the workspaces' thumbnails if we don't use them to declutter the screen. I guess it would be not that hard to implement by inspecting the code of the "Hide Activities Button" extension.

Describe the solution you'd like
Add a toggle in the prefs page to hide the "Activities" button (maybe in Layout page, under the "Panel" group?).

Describe alternatives you've considered
Using another extension, but I like the fact V-Shell gathers a lot of features dispatched in other extensions.