Add go to implementation shortcut (zed-industries#9837)

This adds a keybinding for an existing action. Notably, our bindings for
`Go To Type Definition` and `Go To Implementation` are swapped from
VSCode. We use `cmd` and `shift`, they use `shift` and `cmd`.

Release Notes:

- Added a keybinding for `editor::GoToImplementation`

assets/keymaps/default-linux.json

@@ -74,7 +74,7 @@
       // "cmd-left": "editor::MoveToBeginningOfLine",
       // "ctrl-a": "editor::MoveToBeginningOfLine",
       // "cmd-right": "editor::MoveToEndOfLine",
-      // "ctrl-e": "editor::MoveToEndOfLine", 
+      // "ctrl-e": "editor::MoveToEndOfLine",
       "ctrl-home": "editor::MoveToBeginning",
       "ctrl-end": "editor::MoveToEnd",
       "shift-up": "editor::SelectUp",
@@ -345,6 +345,7 @@
       "f12": "editor::GoToDefinition",
       "alt-f12": "editor::GoToDefinitionSplit",
       "ctrl-f12": "editor::GoToTypeDefinition",
+      "shift-f12": "editor::GoToImplementation",
       "alt-ctrl-f12": "editor::GoToTypeDefinitionSplit",
       "alt-shift-f12": "editor::FindAllReferences",
       "ctrl-m": "editor::MoveToEnclosingBracket",

assets/keymaps/default-macos.json

@@ -366,6 +366,7 @@
       "f12": "editor::GoToDefinition",
       "alt-f12": "editor::GoToDefinitionSplit",
       "cmd-f12": "editor::GoToTypeDefinition",
+      "shift-f12": "editor::GoToImplementation",
       "alt-cmd-f12": "editor::GoToTypeDefinitionSplit",
       "alt-shift-f12": "editor::FindAllReferences",
       "ctrl-m": "editor::MoveToEnclosingBracket",