Update README & add usage

README.md

@@ -7,11 +7,11 @@
 
 ## Introduction
 
-`fastapi-cache` is a tool to cache fastapi response and function result, with backends support `redis` and `memcache`.
+`fastapi-cache` is a tool to cache fastapi response and function result, with backends support `redis`, `memcache`, and `dynamodb`.
 
 ## Features
 
-- Support `redis` and `memcache` and `in-memory` backends.
+- Support `redis`, `memcache`, `dynamodb`, and `in-memory` backends.
 - Easily integration with `fastapi`.
 - Support http cache like `ETag` and `Cache-Control`.
 
@@ -20,6 +20,7 @@
 - `asyncio` environment.
 - `redis` if use `RedisBackend`.
 - `memcache` if use `MemcacheBackend`.
+- `aiobotocore` if use `DynamoBackend`.
 
 ## Install
 
@@ -39,6 +40,12 @@ or
 > pip install "fastapi-cache2[memcache]"
 ```
 
+or
+
+```shell
+> pip install "fastapi-cache2[dynamodb]"
+```
+
 ## Usage
 
 ### Quick Start