update readme

README.md

@@ -30,6 +30,15 @@ two subkeys:
     - `region` - the AWS region (default: **us-east-1**)
     - `version` - the service version (default: **latest**)
     - no other options are available, if you need to configure more, please create and assign custom `client_service`
+- `encoder` - contains the settings for encoders:
+    - `service` - the service which will be used as the encoder
+        - can be one of built-in services (`rikudou.dynamo_cache.encoder.serialize`, `rikudou.dynamo_cache.encoder.json`)
+        - can be a custom service implementing the `\Rikudou\DynamoDbCache\Encoder\CacheItemEncoderInterface` interface
+        - default value: **rikudou.dynamo_cache.encoder.serialize**
+    - `json_options` - settings for the json encoder, ignored if another encoder is used
+        - `encode_flags` - the same flags you would pass to `json_encode()`
+        - `decode_flags` - the same flags you would pass to `json_decode()`
+        - `depth` - the depth argument for both `json_encode()` and `json_decode()`
 - `primary_key_field` - the name of the field that will be used as the primary key (default: **id**)
 - `ttl_field` - the name of the field that will be used as the ttl field (default: **ttl**)
 - `value_field` - the name of the field that will be used as the value field (default: **value**)