Add keybinding to swap pane items (#15583)

- Rearrange tabs (left: `ctrl-shift-pageup`, right: `ctrl-shift-pagedown`) like Chrome

Co-authored-by: Peter Tripp <peter@zed.dev>

assets/keymaps/default-linux.json

@@ -245,6 +245,8 @@
     "bindings": {
       "ctrl-pageup": "pane::ActivatePrevItem",
       "ctrl-pagedown": "pane::ActivateNextItem",
+      "ctrl-shift-pageup": "pane::SwapItemLeft",
+      "ctrl-shift-pagedown": "pane::SwapItemRight",
       "ctrl-w": "pane::CloseActiveItem",
       "ctrl-f4": "pane::CloseActiveItem",
       "alt-ctrl-t": "pane::CloseInactiveItems",

assets/keymaps/default-macos.json

@@ -285,6 +285,8 @@
       "cmd-}": "pane::ActivateNextItem",
       "alt-cmd-left": "pane::ActivatePrevItem",
       "alt-cmd-right": "pane::ActivateNextItem",
+      "ctrl-shift-pageup": "pane::SwapItemLeft",
+      "ctrl-shift-pagedown": "pane::SwapItemRight",
       "cmd-w": "pane::CloseActiveItem",
       "alt-cmd-t": "pane::CloseInactiveItems",
       "ctrl-alt-cmd-w": "workspace::CloseInactiveTabsAndPanes",