feat: support decreasing/increasing fontSize via keyboard (#4553)

Co-authored-by: david <dw@dw.local>

src/actions/types.ts

@@ -101,7 +101,9 @@ export type ActionName =
   | "flipVertical"
   | "viewMode"
   | "exportWithDarkMode"
-  | "toggleTheme";
+  | "toggleTheme"
+  | "increaseFontSize"
+  | "decreaseFontSize";
 
 export type PanelComponentProps = {
   elements: readonly ExcalidrawElement[];