feat: multimode keymap

[fecet]

I'm in the process of migrating my Neovim configuration and I have many nomode keymaps in VimL like:

noremap J=5j

This applies the keymap in "n", "v", and "o" modes. To achieve the same effect in bind.nvim_load_mapping, I currently have to write:

["n|J"] = map_cmd("5j"):with_silent():with_noremap():with_desc("long j"),
["v|J"] = map_cmd("5j"):with_silent():with_noremap():with_desc("long j"),
["o|J"] = map_cmd("5j"):with_silent():with_noremap():with_desc("long j"),

This appears to be very cumbersome and unnecessary. Therefore, I created this PR so we can write:

["nvo|J"] = map_cmd("5j"):with_silent():with_noremap():with_desc("long j"),

Please review this PR and let me know your thoughts.

[CharlesChiuGit]

This is great! Similar to native neovim vim.keymap.set syntax, it can reduce lots of boilerplate. Will test soon.

[CharlesChiuGit]

LGTM

[CharlesChiuGit]

Small reminder. It would be better to use feat/multimode-keymap instead of just multimode-keymap for the branch name.