packages,plugins: add package documentation

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

plugins/cost-insights/api-report.md

@@ -829,6 +829,4 @@ export interface UnlabeledDataflowData {
 // src/api/CostInsightsApi.d.ts:83:8 - (tsdoc-param-tag-missing-hyphen) The @param block should be followed by a parameter name and then a hyphen
 // src/api/CostInsightsApi.d.ts:84:8 - (tsdoc-param-tag-missing-hyphen) The @param block should be followed by a parameter name and then a hyphen
 // src/api/CostInsightsApi.d.ts:100:8 - (tsdoc-param-tag-missing-hyphen) The @param block should be followed by a parameter name and then a hyphen
-
-// (No @packageDocumentation comment for this package)
 ```

plugins/cost-insights/src/index.ts

@@ -14,6 +14,12 @@
  * limitations under the License.
  */
 
+/**
+ * A Backstage plugin that helps you keep track of your cloud spend
+ *
+ * @packageDocumentation
+ */
+
 export {
   costInsightsPlugin,
   costInsightsPlugin as plugin,