feat: add toggle suspend linting

[davidlday]

Closes #750

[Prodeguerriero]

Hi @davidlday

First off, thanks a lot for this!

I finally got around to taking this for a spin. I have two remarks:

• If the linter has detected a problem on the file I am working on, setting the toggle to off does not force the linter to "purge" the list of problems. Instead, I have to close the file and open it again. Is this by design?
• The notification icon in the bottom bar does not appear to react to the toggle. It would be handy to have this icon react, as a quick way of knowing if the linter is currently disabled.

[davidlday]

@Prodeguerriero - thanks for the feedback!

• Regarding purging of the list of problems, that was an oversight, not a design choice. Feel free to open an issue, or I can get one opened later today or tomorrow.
• Same with the icon being non-reactive to the toggle. The tooltip should show it's only enabled for "On Demand", but assuming you would like to see the icon actually change to something different. Again, feel free to open an issue, or I'll try to do so myself later.