Change step back shortcut in command palette to Shift+Backspace (#5604)

* Change cmdbar step back shortcut to Shift+Backspace

* Add visual button for step back

* Make the shortcut apply no matter what's in the input

src/components/CommandBar/CommandBarKclInput.tsx

@@ -146,14 +146,10 @@ function CommandBarKclInput({
           },
         },
         {
-          key: 'Backspace',
-          run: (editor) => {
-            // Only step back if the editor is empty
-            if (editor.state.doc.toString() === '') {
-              stepBack()
-              return true
-            }
-            return false
+          key: 'Shift-Backspace',
+          run: () => {
+            stepBack()
+            return true
           },
         },
       ]),