packages,plugins: add package documentation

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

packages/version-bridge/api-report.md

@@ -45,6 +45,4 @@ export type VersionedValue<
     version: Version,
   ): Versions[Version] | undefined;
 };
-
-// (No @packageDocumentation comment for this package)
 ```

packages/version-bridge/src/index.ts

@@ -14,4 +14,10 @@
  * limitations under the License.
  */
 
+/**
+ * Utilities used by Backstage packages to support multiple concurrent versions
+ *
+ * @packageDocumentation
+ */
+
 export * from './lib';