Add example for tracing require()s

Signed-off-by: Darshan Sen <[email protected]>

docs/examples/tracing-requires/.gitignore

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+events.json
+node_modules

docs/examples/tracing-requires/README.md

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+# Tracing `require()`s
+
+A new `TraceEvents` object is created in:
+
+TODO
+
+Before the process exits, the `TraceEvents` object is destroyed and the trace events are stringified and printed to `events.json` in:
+
+TODO
+
+The code that needs to be profiled can be done using the `peformance.measure()` and `peformance.mark()` APIs from [Node.js](https://nodejs.org/api/perf_hooks.html#performancemarkname-options) and the [Web](https://www.w3.org/TR/user-timing):
+
+```js
+peformance.mark("before");
+// code that needs to be profiled
+performance.measure("after", "before");
+```
+
+like it's being done in:
+
+TODO
+
+After running `node .`, the generated `events.json` file can be opened on [https://ui.perfetto.dev](https://ui.perfetto.dev) for visualization:
+
+![](./perfetto.png)

docs/examples/tracing-requires/index.js

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+const { TraceEvents, trackRequires } = require("../../..");
+const { writeFileSync } = require('fs');
+
+const traceEvents = new TraceEvents();
+
+process.on("beforeExit", () => {
+  const events = traceEvents.getEvents();
+  traceEvents.destroy();
+  writeFileSync("events.json", JSON.stringify(events));
+});
+
+trackRequires(true);
+
+// Express Hello world example
+// Refs: https://expressjs.com/en/starter/hello-world.html
+const express = require('express');
+const app = express();
+const port = 3000;
+
+let server;
+
+app.get('/', (req, res) => {
+  res.send('Hello World!');
+  server.close();
+});
+
+server = app.listen(port, () => {
+  console.log(`Example app listening on port ${port}`);
+});