feat(workspace): allow alternative actions to open files and symbols in split

Co-authored-by: Mikayla Maki <mikayla@zed.dev>

assets/keymaps/default.json

@@ -13,6 +13,7 @@
       "cmd-up": "menu::SelectFirst",
       "cmd-down": "menu::SelectLast",
       "enter": "menu::Confirm",
+      "cmd-enter": "menu::SecondaryConfirm",
       "escape": "menu::Cancel",
       "ctrl-c": "menu::Cancel",
       "cmd-{": "pane::ActivatePrevItem",
@@ -298,7 +299,9 @@
       "shift-f8": "editor::GoToPrevDiagnostic",
       "f2": "editor::Rename",
       "f12": "editor::GoToDefinition",
+      "alt-f12": "editor::GoToDefinitionSplit",
       "cmd-f12": "editor::GoToTypeDefinition",
+      "alt-cmd-f12": "editor::GoToTypeDefinitionSplit",
       "alt-shift-f12": "editor::FindAllReferences",
       "ctrl-m": "editor::MoveToEnclosingBracket",
       "alt-cmd-[": "editor::Fold",