chore(README): add examples and update roadmap

README.md

@@ -7,10 +7,98 @@ APIs similar to the source repository.
 
 Only libsignal-protocol is implemented at this time.
 
-This repository is still under development, so
-breaking changes should be expected.
+This repository is still under development, so users should expect
+breaking changes.
+
+## How to Use
+
+### Protocol
+
+#### Session
+
+```go
+package main
+
+import (
+	"context"
+	"crypto/rand"
+
+	"github.com/RTann/libsignal-go/protocol/address"
+	"github.com/RTann/libsignal-go/protocol/identity"
+	"github.com/RTann/libsignal-go/protocol/session"
+)
+
+// Alice creates a session with Bob and sends a message.
+// Error handing is ignored in this example, but should otherwise not be ignored.
+func main() {
+	keyPair, _ := identity.GenerateKeyPair(rand.Reader)
+	registrationID := uint32(1)
+    bobAddress := address.Address{
+        Name:     "+15555555555",
+        DeviceID: 1,
+    }
+
+    // Alice creates a session to talk to Bob.
+    aliceSession := &session.Session{
+        RemoteAddress:    bobAddress,
+        SessionStore:     session.NewInMemStore(),
+        IdentityKeyStore: identity.NewInMemStore(keyPair, registrationID),
+    }
+	// Write a nice encrypted message to Bob.
+	plaintext := []byte("Hello, Bob!")
+	aliceCiphertext, _ := aliceSession.EncryptMessage(context.Background(), plaintext)
+
+	// Alice sends her encrypted message to Bob.
+}
+```
+
+```go
+package main
+
+import (
+	"context"
+	"crypto/rand"
+
+	"github.com/RTann/libsignal-go/protocol/address"
+	"github.com/RTann/libsignal-go/protocol/identity"
+	"github.com/RTann/libsignal-go/protocol/session"
+)
+
+// Bob creates a session with Alice and receives a message.
+// Error handing is ignored in this example, but should otherwise not be ignored.
+func main() {
+	keyPair, _ := identity.GenerateKeyPair(rand.Reader)
+	registrationID := uint32(1)
+    aliceAddress := address.Address{
+        Name:     "+15555555556",
+        DeviceID: 1,
+    }
+
+    // Bob creates a session to talk to Alice.
+    bobSession := &session.Session{
+        RemoteAddress:    bobAddress,
+        SessionStore:     session.NewInMemStore(),
+        IdentityKeyStore: identity.NewInMemStore(keyPair, registrationID),
+    }
+
+	var ciphertext []byte
+	// Bob receives Alice's message and stores it in ciphertext.
+
+	plaintext, _ := bobSession.DecryptMessage(context.Background(), rand.Reader, ciphertext)
+
+	// Alice sends her encrypted message to Bob.
+}
+```
+
+#### Group Session
+
+```go
+
+```
 
 ## Roadmap
 
-* Add and refactor tests
-* Implement other APIs available in the source repository.
+1. Implement post-quantum cryptography support.
+1. Implement sealed sender support.
+1. Add and refactor tests.
+1. Implement other APIs available in the source repository.