vim: Add indent-wise motions (#28044)

Taken from:
https://github.com/jeetsukumaran/vim-indentwise?tab=readme-ov-file#movements-by-relative-indent-depth



> [- : Move to previous line of lesser indent than the current line.
> [+ : Move to previous line of greater indent than the current line.
> [= : Move to previous line of same indent as the current line that is
separated from the current line by lines of different indents.
> ]- : Move to next line of lesser indent than the current line.
> ]+ : Move to next line of greater indent than the current line.
> ]= : Move to next line of same indent as the current line that is
separated from the current line by lines of different indents.



Release Notes:

- vim: Added indent-wise motions `] -/+/=`

assets/keymaps/vim.json

@@ -44,6 +44,12 @@
       "[ /": "vim::PreviousComment",
       "] *": "vim::NextComment",
       "] /": "vim::NextComment",
+      "[ -": "vim::PreviousLesserIndent",
+      "[ +": "vim::PreviousGreaterIndent",
+      "[ =": "vim::PreviousSameIndent",
+      "] -": "vim::NextLesserIndent",
+      "] +": "vim::NextGreaterIndent",
+      "] =": "vim::NextSameIndent",
       // Word motions
       "w": "vim::NextWordStart",
       "e": "vim::NextWordEnd",