message: Add documentation for github-discovery processor
diff: @@ -79,6 +79,38 @@ silently at startup for convenience. So you only have to list it if you want to
  supply a token for it - and if you do, you can also leave out the `apiBaseUrl`
  and `rawBaseUrl` fields.
  +### Processor: github-discovery
  +
  +There is a special GitHub discovery processor for discovering catalog entities
  +within a GitHub organization. The processor will crawl a given GitHub
  +organization and register entities matching the configured path. This can be
  +useful as an alternative to static locations or manually adding things to the
  +catalog.
  +
  +To use the discovery processor, you'll need a GitHub integration set up as above
  +with a `GITHUB_TOKEN`. Then you can add a location target to the catalog
  +configuration:
  +
  +```yaml
  +catalog:
  + locations:
  + - type: github-discovery
  + target: https://github.com/myorg/service-*/blob/main/catalog-info.yaml
  +```
  +
  +Note the `github-discovery` type, as this is not a regular `url` processor.
  +
  +The target is composed of three parts:
  +
  +- The base organization URL, `https://github.com/myorg` in this case
  +- The repository blob to scan, which accepts \* wildcard tokens. This can simply
  + be `*` to scan all repositories in the organization. This example only looks
  + for repositories prefixed with `service-`.
  +- The path within each repository to find the catalog YAML file. This will
  + usually be `/blob/main/catalog-info.yaml`, `/blob/master/catalog-info.yaml` or
  + a similar variation for catalog files stored in the root directory of each
  + repository.
  +
  ## Static Location Configuration
  To enable declarative catalog setups, it is possible to add locations to the
  