docs: add FS storage to docs (#7681)

Author: cbaker6

README.md

@@ -489,11 +489,12 @@ You can also find more adapters maintained by the community by searching on [npm
 
 Parse Server allows developers to choose from several options when hosting files:
 
-* `GridFSBucketAdapter`, which is backed by MongoDB;
-* `S3Adapter`, which is backed by [Amazon S3](https://aws.amazon.com/s3/); or
-* `GCSAdapter`, which is backed by [Google Cloud Storage](https://cloud.google.com/storage/)
+* `GridFSBucketAdapter` - which is backed by MongoDB
+* `S3Adapter` - which is backed by [Amazon S3](https://aws.amazon.com/s3/)
+* `GCSAdapter` - which is backed by [Google Cloud Storage](https://cloud.google.com/storage/)
+* `FSAdapter` - local file storage
 
-`GridFSBucketAdapter` is used by default and requires no setup, but if you're interested in using S3 or Google Cloud Storage, additional configuration information is available in the [Parse Server guide](http://docs.parseplatform.org/parse-server/guide/#configuring-file-adapters).
+`GridFSBucketAdapter` is used by default and requires no setup, but if you're interested in using Amazon S3, Google Cloud Storage, or local file storage, additional configuration information is available in the [Parse Server guide](http://docs.parseplatform.org/parse-server/guide/#configuring-file-adapters).
 
 ## Idempotency Enforcement