Add "shift-r" and "g ." support for helix mode (#35468)

Related #4642
Compatible with #34136

Release Notes:

- Helix: `Shift+R` works as Paste instead of taking you to ReplaceMode
- Helix: `g .` goes to last modification place (similar to `. in vim)

assets/keymaps/vim.json

@@ -428,11 +428,13 @@
       "g h": "vim::StartOfLine",
       "g s": "vim::FirstNonWhitespace", // "g s" default behavior is "space s"
       "g e": "vim::EndOfDocument",
+      "g .": "vim::HelixGotoLastModification", // go to last modification
       "g r": "editor::FindAllReferences", // zed specific
       "g t": "vim::WindowTop",
       "g c": "vim::WindowMiddle",
       "g b": "vim::WindowBottom",
 
+      "shift-r": "editor::Paste",
       "x": "editor::SelectLine",
       "shift-x": "editor::SelectLine",
       "%": "editor::SelectAll",