[RFE] avy-goto-char* allow start of line, first non-whitespace, end of line targets via arrow keys

[Lenbok]

I am a new user of avy and as part of getting similar capability in the other editor I use (IntelliJ IDE), I have installed an acejump-like plugin from https://github.com/johnlindquist/AceJump. The AceJump IntelliJ plugin has a nice feature that I think would be quite useful in avy.

After activating the jump mode, if you press the left, up, or right arrow keys instead of a regular character, these serve to set the jump targets to the start of line (i.e. equivalent to avy-goto-line), first non-whitespace (not currently possible with avy?), and end of line positions respectively (not currently possible with avy?). There is a screenshot towards the end of https://github.com/johnlindquist/AceJump/blob/master/README.md

[Lenbok]

The same left, up, right arrow keys also work in their equivalent of avy-goto-line, so it might also (or alternatively) make sense to also add this capability to avy-goto-line (similarly to how pressing a digit currently takes you to line-number entry).

[abo-abo]

See avy-dispatch-alist. You can customize that to do what you want. Maybe even open a PR to extend the defaults.