docs: add rough readme

README.md

@@ -1,3 +1,64 @@
 # yamcs-protobufjs-static
 
-WIP
+This package provides protobufjs definitions and typings for YAMCS.
+
+To use:
+
+```js
+// Import the package
+import { google, yamcs } from 'yamcs-protobufjs-static';
+
+// Extract the needed types
+const { SubscribeParametersRequest } = yamcs.protobuf.processing;
+const { ClientMessage, CancelOptions } = yamcs.api;
+const { Any } = google.protobuf;
+
+const socket = new WebSocket('ws://localhost:8090/', 'protobuf');
+socket.binaryType = 'arraybuffer';
+
+let connected = false;
+
+socket.onopen = () => {
+    connected = true;
+}
+
+// Example of subscribing to a parameter
+const id = [yamcs.protobuf.NamedObjectId.create({ name: 'myNamedObject'})];
+const message = {
+    type: 'parameters',
+    instance: 'myInstance',
+    processor: 'myProcessor',
+    id,
+    sendFromCache: true,
+    updateOnExpiration: true
+};
+
+// Verify that it fits the schema of a `SubscribeParametersRequest`
+let err = SubscribeParametersRequest.verify(message);
+if (err) {
+    throw Error(err);
+}
+
+let payload = SubscribeParametersRequest.create(message);
+const arrayBuffer = SubscribeParametersRequest.encode(payload).finish();
+const clientMessagePayload = {
+    type: dataType,
+    id: subscriptionId,
+    options: Any.create({
+        type_url: SubscribeParametersRequest.getTypeUrl(),
+        value: arrayBuffer
+    })
+};
+
+// Verify that it fits the schema of a `ClientMessage`
+err = ClientMessage.verify(clientMessagePayload);
+if (err) {
+    throw Error(err);
+}
+
+const clientMessage = ClientMessage.create(clientMessagePayload);
+
+if(connected) {
+    socket.send(ClientMessage.encode(clientMessage).finish());
+}
+```