packages,plugins: add package documentation

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

plugins/techdocs-backend/src/index.ts

@@ -14,6 +14,12 @@
  * limitations under the License.
  */
 
+/**
+ * The Backstage backend plugin that renders technical documentation for your components
+ *
+ * @packageDocumentation
+ */
+
 export { createRouter } from './service/router';
 export * from './search';
 export * from '@backstage/techdocs-common';