Add documentation for Tasks Settings

[claremacrae]

These are the current options:

More will be coming soon, as some older pull requests are merged.

Suggest it goes next to wherever #754 docs get added.

[AnnaKornfeldSimpson]

Does a page for Tasks Settings within the "Getting Started" section seems reasonable? The ones pictured here can be documented there, linking to the global filter page as appropriate. The auto-suggest ones are already documented on that page, so the Settings documentation page could just link to that.

[claremacrae]

Does a page for Tasks Settings within the "Getting Started" section seems reasonable? The ones pictured here can be documented there, linking to the global filter page as appropriate. The auto-suggest ones are already documented on that page, so the Settings documentation page could just link to that.

Yes that was the kind of thing I had in mind. And links are good!

Screenshots need to be from a light theme, with as little useless space as possible, and the text large, for maximum readability for those with poor eye sight.