Add more documentation

packages/plugins/analytics/README.md

@@ -1,3 +1,30 @@
 # Analytics Plugin <!-- #omit in toc -->
 
 Send some analytics data to Datadog internally.
+
+It gives you acces to the `context.sendLog()` function.
+
+```typescript
+// Send a basic log.
+context.sendLog('My basic log');
+
+// Send some context with the log.
+context.sendLog('My contextual log', { some: 'context' });
+```
+
+Every log already has some context to it:
+
+```typescript
+{
+    ddsource: string; // Name of the bundler plugin (e.g. `@datadog/webpack-plugin`).
+    env: Env; // Environment (e.g. `production`).
+    message; // The log message.
+    service: 'build-plugins';
+    bundler: {
+        name: string; // Name of the bundler (e.g. `webpack`).
+        version: string; // Version of the bundler.
+    };
+    plugins: PluginName[]; // List of the plugins/features enabled.
+    version: string; // Version of the plugin.
+}
+```