Shortcut for faster tool switching

[philippotto]

I think (1) should be prioritized.

1) Fast switching to tools via dedicated shortcuts

See https://scm.slack.com/archives/C5AKLAV0B/p1683099934581439?thread_ts=1683097839.871459&cid=C5AKLAV0B
Something like:

• ctrl + k, b -> selects brush
• ctrl + k, e -> selects eraser
• ...

2) Fast switching between two tools via one shortcut

When annotating data, some users would like to switch between tools with a shortcut (which would be assigned to buttons on a digital pen). The existing w/shift+w shortcut is not very predictable.

I see two options:
a) have a shortcut which switches to the most recently used tool (similar to alt+tab)
b) have a shortcut which switches to the "pendant" (brush <-> brush eraser, lasso <-> lasso eraser, $otherTools <-> move-tool)

I think (a) is the most intuitive (and generic) one, but requires a "set up" by activating the two tools between one wants to switch.

As a shortcut, I suggest "X". This is slightly similar to how Photoshop/GIMP where X switches foreground and background color.