Add Sentry usage to ESM docs

Author: timokoessler

docs/esm.md

@@ -31,6 +31,26 @@ node --env-file=.env -r @aikidosec/firewall/instrument your-app.js
 > [!NOTE]
 > The `--env-file` flag cannot be used in `NODE_OPTIONS`.
 
+## Use Zen together with Sentry (ESM)
+
+You need to use Node.js v24.11.1 / v25.1.0 or later to use Zen together with Sentry in an ESM application.
+Follow the [Sentry instructions for ESM](https://docs.sentry.io/platforms/javascript/guides/node/install/esm/) to set up Sentry. After that, add the Zen import inside the `instrument.mjs` file as shown below.
+
+```js
+import "@aikidosec/firewall/instrument";
+import * as Sentry from "@sentry/node";
+
+Sentry.init({
+  // ...
+});
+```
+
+Import the `instrument.mjs` file using the `--import` flag when starting your application. The `-r @aikidosec/firewall/instrument` CLI flag is not needed in this case.
+
+```sh
+node --import ./instrument.mjs your-app.js
+```
+
 ## Known issues
 
 - Zen can not protect ESM sub-dependencies of an ESM package. For example if an ESM package `foo` imports a sub-dependency `bar` that is also an ESM package, Zen will not be able to protect the code in `bar`. This is because the V8 engine does not allow Node.js to observe the evaluation of inner ESM packages (yet). Open issue: [Adding an evaluation hook for v8::Module](https://issues.chromium.org/u/1/issues/384413088). See a full example below.