chore: add changeset

Signed-off-by: blam <ben@blam.sh>

.changeset/dry-squids-tap.md

@@ -0,0 +1,26 @@
+---
+'@backstage/frontend-plugin-api': patch
+---
+
+Introduce a new way to create extension types and kinds, with `createExtensionKind`.
+
+This allows the creation of extension with the following pattern:
+
+```tsx
+// create the extension kind
+const TestExtension = createExtensionKind({
+  kind: 'test-extension',
+  attachTo: { id: 'test', input: 'default' },
+  output: {
+    element: coreExtensionData.reactElement,
+  },
+  factory(_, props: { text: string }) {
+    return {
+      element: <h1>{props.text}</h1>,
+    };
+  },
+});
+
+// create an instance of the extension kind with props
+const testExtension = TestExtension.create({ text: 'Hello World' });
+```