add license and docs about encoding support

README.md

@@ -2,6 +2,41 @@
 
 Binary Field Encodings (BFE) for Secure Scuttlebutt (SSB).
 
+See the [SSB Binary Field Encodings Specification](https://github.com/ssbc/ssb-bfe-spec) for details.
+
+## Encoding
+
+```elixir
+SsbBfe.encode(value)
+```
+
+### Elixir Types
+
+Encoding of the following Elixir types is supported:
+
+ - List
+ - Map
+ - Tuple
+ - String
+ - Boolean
+ - Nil
+ - Integer
+ - Float
+
+Note: encoding of structs is not supported. You may wish to convert your struct to amap and encode it that way.
+
+### Scuttlebutt Types
+
+Encoding of the following Scuttlebutt types is supported:
+
+ - Feed (classic)
+ - Message (classic)
+ - Blob
+ - Signature
+ - Private message (box, box2)
+
+Note: encoding of URIs is not currently supported, nor are other formats such as Gabby Grove and Bendy Butt.
+
 ## Installation
 
 If [available in Hex](https://hex.pm/docs/publish), the package can be installed
@@ -15,7 +50,12 @@ def deps do
 end
 ```
 
+## Documentation
+
 Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
 and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
 be found at <https://hexdocs.pm/ssb_bfe>.
 
+## License
+
+LGPL-3.0.