Update readme

Author: rpidanny

README.md

@@ -1 +1,18 @@
-# ffmpeg-lambda-layer
+# ffmpeg-lambda-layer
+
+AWS Lambda layer with ffmpeg binaries.
+
+## Included Codecs
+
+- `x264`
+- `x265`
+- `aac`
+- `mp3`
+- `opus`
+- `vpx`
+
+## Version ARNs
+
+| Ffmpeg version | ARN |
+| --- | --- |
+| 4.1.3 | `arn:aws:lambda:<region>:175033217214:layer:ffmpeg:1` |