Feat: Add ability to change calendar mappings

[kristijanhusak]

Discussed in #971

^{Originally posted by Patitotective April 24, 2025}
Hi, I was wondering whether it was possible to change the default calendar mappings. I find it rather difficult to type <> and was wondering whether it was possible to remap them to something more easier to type (and remember) like fb (for month forward and month backward).
Thanks.

[epirus]

I think < > are beautiful