frontend-test-utils: README + doc cleanup

Co-authored-by: Camila Belo <camilaibs@gmail.com>
Co-authored-by: Fredrik Adelöw <freben@gmail.com>
Co-authored-by: Philipp Hugenroth <philipph@spotify.com>
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/bright-eyes-film.md

@@ -2,4 +2,4 @@
 '@backstage/frontend-test-utils': minor
 ---
 
-New testing utility library for `@backstage/frontend-app-api` and `@backstagr/frontend-plugin-api`.
+New testing utility library for `@backstage/frontend-app-api` and `@backstage/frontend-plugin-api`.

packages/frontend-test-utils/README.md

@@ -1,12 +1,12 @@
 # @backstage/frontend-test-utils
 
-_This package was created through the Backstage CLI_.
+Contains utilities that can be used when testing frontend features such as extensions.
 
 ## Installation
 
-Install the package via Yarn:
+Install the package via Yarn into your own packages:
 
 ```sh
 cd <package-dir> # if within a monorepo
-yarn add @backstage/frontend-test-utils
+yarn add --dev @backstage/frontend-test-utils
 ```

packages/frontend-test-utils/api-report.md

@@ -27,6 +27,4 @@ export class ExtensionTester {
   // (undocumented)
   render(options?: { config?: JsonObject }): RenderResult;
 }
-
-// (No @packageDocumentation comment for this package)
 ```

packages/frontend-test-utils/src/index.ts

@@ -14,4 +14,10 @@
  * limitations under the License.
  */
 
+/**
+ * @packageDocumentation
+ *
+ * Contains utilities that can be used when testing frontend features such as extensions.
+ */
+
 export * from './app';