Add which-key support

[fbrosda]

This adds support for the which-key-mode based on the advice in justbur/emacs-which-key#353 (comment)

It reuses most parts of the original implementation found in https://github.com/justbur/emacs-which-key/pull/353/files and adjusts it for the changes made in justbur/emacs-which-key@5fbdf05

Related Issue: #3

[subnut]

I think this depends upon the order in which which-key-mode and devil-mode are enabled?

In my (admittedly short) testing, it seems that loading which-key after devil-mode has already been enabled causes ,x to NOT trigger the which-key page for C-x

Can you reproduce this issue?
(I'm on Emacs 30.1, in case that's relevant.)

[fbrosda]

Can you reproduce this issue?

Yes, the problem was, that the code only used bound-and-true-p to check, if which-key is currently defined and active. I adjusted it, to also use the which-key-mode-hook, so now the which-key support should be enabled independent of the order in which you activate the two modes.

[subnut]

umm... now it seems to break disastrously when I do M-x global-devil-mode without enabling which-key-mode first?
i.e. I cannot even do M-x anymore.. it shows this error --

Symbol’s value as variable is void: which-key-this-command-keys-function

[fbrosda]

oh, sorry, I did not test, when which-key was not loaded at all. Please try again.

[subnut]

Upon light testing, it seems to be working properly now. Thanks!