feat: add command shortcut keys to convert text to title (#921)

* feat: add command shortcut keys to convert text to title

* fix: use const values from heading block keys

* chore: add test cases for command

* fix: comments and nomenclature

* chore: add appropriate description

lib/src/l10n/l10n.dart

@@ -1840,6 +1840,46 @@ class AppFlowyEditorLocalizations {
       args: [],
     );
   }
+
+  /// `toggle H1`
+  String get cmdToggleH1 {
+    return Intl.message(
+      'toggle H1',
+      name: 'cmdToggleH1',
+      desc: '',
+      args: [],
+    );
+  }
+
+  /// `toggle H2`
+  String get cmdToggleH2 {
+    return Intl.message(
+      'toggle H2',
+      name: 'cmdToggleH2',
+      desc: '',
+      args: [],
+    );
+  }
+
+  /// `toggle H3`
+  String get cmdToggleH3 {
+    return Intl.message(
+      'toggle H3',
+      name: 'cmdToggleH3',
+      desc: '',
+      args: [],
+    );
+  }
+
+  /// `toggle body`
+  String get cmdToggleBody {
+    return Intl.message(
+      'toggle body',
+      name: 'cmdToggleBody',
+      desc: '',
+      args: [],
+    );
+  }
 }
 
 class AppLocalizationDelegate