draft: add oer finder plugin

[JannikStreek]

Description

Adds the oer finder plugin to the project to fetch images from the aggregator.

• Set a GITHUB_TOKEN env variable before installing, as this is required for access to the package registry on GitHub
• To make this work for you, you will need a running aggregator instance with inserted content. You can use the example here: https://oer-finder-plugin.osc-fr1.scalingo.io with docs located here: OER API Doku. However, keep in mind there is not much content yet and and it does not offer imgproxy support. Imgproxy makes a lot of sense but is a bit more work to host as it requires a running docker container. That is why I am running everything locally for now.

[hugotiburtino]

Where to configure the backend for the aggregator? Currently hardcoded

In static/config.json (please update also config.example.json) (as far as I can see, there is no secret involved, so it may be ok do the configuration in a public file)

[JannikStreek]

Where to configure the backend for the aggregator? Currently hardcoded

In static/config.json (please update also config.example.json) (as far as I can see, there is no secret involved, so it may be ok do the configuration in a public file)

thanks, added the defaults