chore(otel): Add basic usage instructions to readme (#6094)

Author: mydea

packages/opentelemetry-node/README.md

@@ -10,6 +10,44 @@
 [![npm dm](https://img.shields.io/npm/dm/@sentry/opentelemetry-node.svg)](https://www.npmjs.com/package/@sentry/opentelemetry-node)
 [![npm dt](https://img.shields.io/npm/dt/@sentry/opentelemetry-node.svg)](https://www.npmjs.com/package/@sentry/opentelemetry-node)
 
+## Installation
+
+```bash
+npm install @sentry/node @sentry/opentelemetry-node
+
+# Or yarn
+yarn add @sentry/node @sentry/opentelemetry-node
+```
+
+Note that `@sentry/opentelemetry-node` depends on the following peer dependencies:
+
+* `@opentelemetry/api` version 1 or greater
+* `@opentelemetry/sdk-trace-base` version 1 or greater, or a package that implements that, like `@opentelemetry/sdk-node`.
+
+## Usage
+
+You need to register the SentrySpanProcessor with your OpenTelemetry installation:
+
+```js
+import * as Sentry from '@sentry/node';
+import { SentrySpanProcessor } from '@sentry/opentelemetry-node';
+
+// Make sure to call this BEFORE setting up OpenTelemetry
+Sentry.init({
+  dsn: '__DSN__',
+  // ...
+});
+
+const sdk = new opentelemetry.NodeSDK({
+  // Existing config
+  traceExporter: new OTLPTraceExporter(),
+  instrumentations: [ getNodeAutoInstrumentations() ],
+
+  // Sentry config
+  spanProcessor: new SentrySpanProcessor()
+})
+```
+
 ## Links
 
 - [Official SDK Docs](https://docs.sentry.io/quickstart/)