How-to expose plugin to backstage

[adberger]

Is this still up-to-date?
https://github.com/K-Phoen/backstage-plugin-grafana/blob/main/docs/setup.md

I don't have the plugin.tsx file (packages/app/src/plugins.tsx) on a fresh backstage installation.

When setting the annotation in a catalog I get the following error in the logs:
2023-02-03T14:21:34.031Z proxy error [HPM] Error occurred while proxying request localhost:7007/api/search?type=dash-db&tag=kubernetes-mixin to https://grafana.mgmtbi.ch/ [EPROTO] (https://nodejs.org/api/errors.html#errors_common_system_errors) type=plugin