Add binding for find-file-at-point

[carmenbianca]

This is a very simple PR to bind 'SPC f h' to find-file-at-point. This is immensely useful in terminal emulators. 'h' is a mnemonic for 'here'. 'c' and 'C' (for 'cursor') were already taken.

Fix: N/A
Ref: N/A
Close: N/A

---

• I searched the issue tracker and this hasn't been PRed before.
• My changes are not on the do-not-PR list for this project.
• My commits conform to the git conventions.
• Any relevant issues or PRs have been linked to.

[LemonBreezes]

If you are using the :completion vertico module, you can use find-file, and then M-n to select the file name at point. As a general rule, if you are doing minibuffer completion and you type M-n when there are no history items ahead of you, Emacs will try to guess what you are trying to complete. This is called "future history".