- [x] BaseIndexer- modify to be more abstract
- [x] ContentIndexer - add
- [x] RevisionIndexer - add
- [x] RevisionMetadataIndexer
- [ ] tests for indexer (with Mock storage)
- [x] update Readme
- [x ] swh-metadata-detector as tool used by RevisionMetadataIndexer to detect metadata files
and call ContentMetadataIndexer