Add README

README.md

@@ -0,0 +1,28 @@
+Synapse S3 Storage Provider
+===========================
+
+This module can be used by synapse as a storage provider, allowing it to fetch
+and store media in Amazon S3.
+
+
+Usage
+-----
+
+The `s3_storage_provider.py` should be on the PYTHONPATH when starting
+synapse.
+
+Example of entry in synapse config:
+
+```yaml
+media_storage_providers:
+- module: s3_storage_provider.S3StorageProviderBackend
+  store_local: True
+  store_remote: True
+  store_synchronous: True
+  config:
+    bucket: <S3_BUCKET_NAME>
+```
+
+This module uses `boto3`, and so the credentials should be specified as
+described [here](https://boto3.readthedocs.io/en/latest/guide/configuration.html#guide-configuration).
+