packages,plugins: add package documentation

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

plugins/explore-react/api-report.md

@@ -29,6 +29,4 @@ export interface ExploreToolsConfig {
 //
 // @public (undocumented)
 export const exploreToolsConfigRef: ApiRef<ExploreToolsConfig>;
-
-// (No @packageDocumentation comment for this package)
 ```

plugins/explore-react/src/index.ts

@@ -14,4 +14,10 @@
  * limitations under the License.
  */
 
+/**
+ * A frontend library for Backstage plugins that want to interact with the explore plugin
+ *
+ * @packageDocumentation
+ */
+
 export * from './tools';