B.t.w. it does not add much to `pretty-hydra`, maybe I should just have extended pretty hydra,
with a function that simply 'gathers' function names by giving it a list of 'key-strings'.
But I remembered that hydra was not a good option for `sketch-mode` so I wanted to create
this anyway for that package.
And somehow it feels not right to create an extra keymap, just to have a key-guide. But on the
other hand, that could also be just a better approach (that is hard to 'decide' ).
If anyone has some ideas about it, they are very welcome. Otherwise and in any case this is just
very similar to pretty hydra, but without depending on the hydra package and introducing extra
keymaps.