Add key binds to Jump for cycling through tabs and sites.

[lindely]

This PR adds key binds to Jump:

• Pressing T will open or close the tags menu.
• Pressing ↑, ↓, ← or → will cycle through the tags when the tags menu is open.
• When the tags menu is closed, the arrows will cycle through the sites.
• ↑ and ← will both cycle back, whereas ↓ and → will cycle forward.
• Pressing Enter will activate the selected tag or site.
• Pressing Escape will clear selections.
• Pressing Ctrl followed by a number will open the site at that position. For example, Ctrl + 1 will open the site on the first tile, Ctrl + 2 the site on the second tile, and so on. The first ten tiles can be opened this way.

[daledavies]

Nice, thanks! Great idea I'll give it a whirl over the next few days, just had a quick look at the code on my phone and it looks good.

[lindely]

I just noticed I failed to test properly and found some small issues. A fix is on its way, though :-). The next commit will hopefully be solid.

[daledavies]

Awesome, no worries. Thanks again 😁

[lindely]

I committed the fixes. Thanks for taking an interest in the change!

[daledavies]

Thanks for taking an interest in Jump! 🙂

[lindely]

After careful consideration I added a final commit. When switching tags with the keys, it makes sense to start cycling from the active tag instead of always from the first one. I used it myself for a bit and like how it works. If you however dislike this approach, feel free to remove commit 6a5b203.

[lindely]

I forgot about the optional search box. With the last commit, the key binds play nice with it enabled. The escape key now also closes the search box.