add core extensions

packages/core/src/extensions/clearContent.ts

@@ -0,0 +1,18 @@
+import { Command } from '../Editor'
+import { createExtension } from '../Extension'
+
+export const ClearContent = createExtension({
+  addCommands() {
+    return {
+      clearContent: (emitUpdate: Boolean = false): Command => ({ commands }) => {
+        return commands.setContent('', emitUpdate)
+      },
+    }
+  },
+})
+
+declare module '../Editor' {
+  interface AllExtensions {
+    ClearContent: typeof ClearContent,
+  }
+}