chore: update readme

Author: ssut

README.md

@@ -2,6 +2,22 @@
 
 An android OTA payload dumper written in Go.
 
+## Features
+
+![screenshot](https://i.imgur.com/IJtwoWU.png)
+
+- Incredibly fast decompression. All decompression progresses are executed in parallel.
+- Payload checksum verification.
+- Support original zip package that contains payload.bin.
+
+### Cautions
+
+- Working on a SSD is highly recommended for performance reasons, a HDD could be a bottle-neck.
+
+### Limitations
+
+- Incremental OTA(delta) payload is not supported.
+
 ## Sources
 
 https://android.googlesource.com/platform/system/update_engine/+/master/update_metadata.proto