vim: Add Smart Relative Line Number (#16567)

Closes #16514

Release Notes:

- Added Vim: absolute numbering in any mode except `insert` mode

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

docs/src/vim.md

@@ -241,8 +241,17 @@ Some vim settings are available to modify the default vim behavior:
     // "never": don't use system clipboard unless "+ or "* is specified
     // "on_yank": use system clipboard for yank operations when no register is specified
     "use_system_clipboard": "always",
-    // Lets `f` and `t` motions extend across multiple lines
-    "use_multiline_find": true
+    // Let `f` and `t` motions extend across multiple lines
+    "use_multiline_find": true,
+    // Let `f` and `t` motions match case insensitively if the target is lowercase
+    "use_smartcase_find": true,
+    // Use relative line numbers in normal mode, absolute in insert mode
+    // c.f. https://github.com/jeffkreeftmeijer/vim-numbertoggle
+    "toggle_relative_line_numbers": true,
+    // Add custom digraphs (e.g. ctrl-k f z will insert a zombie emoji)
+    "custom_digraphs": {
+      "fz": "🧟‍♀️"
+    }
   }
 }
 ```