Add clarification for otel-js apps written in CJS and ESM

[JamieDanielson]

Node.js has two module systems: CommonJS(CJS) and ECMAScript modules(ESM). As ESM becomes more common in usage, we need to better document the current assumptions and requirements.

This is a start with the bare minimum, which is to specify the assumption that the app is running as CJS... as well as document the loader hook currently required for ESM apps. It seemed useful to start here based on issues like #4812.

More details will follow as we finalize reference docs in the otel-js repo.

[trentm]

Having the h3 section header for this unintentionally puts the subsequent content ("Open http://localhost:8080/rolldice in your web browser ...") under this section.

I don't have a great alternative suggestion. Perhaps the section could be replaced with a much shorter:

(Note: If your application is written in JavaScript as ECMAScript Modules (ESM), or compiled to ESM from TypeScript, then a loader hook is required to properly support instrumentation. Use node --experimental-loader=@opentelemetry/instrumentation/hook.mjs --require ./instrumentation.js app.js. See [the coming reference link in opentelemetry-js/docs/] for details on ESM support.)

[trentm]

Ah... in my suggestion above, I've removed this anchor. Perhaps the "see here for more info" could be the opentelemetry-js/doc/ document that is being added in open-telemetry/opentelemetry-js#4876 instead?

[theletterf]

Thanks! Some comments.

[theletterf]

Suggested change

	Much of OpenTelemetry JS documentation is written assuming the compiled application is run as CommonJS.
	The OpenTelemetry documentation assumes that the compiled application is run as CommonJS.

Would it make sense to add a link to CommonJS? Are all Node developers familiar with it?

[theletterf]

Suggested change

	### Instrumentation for ECMAScript Modules
	### Instrumentation for ECMAScript modules

[theletterf]

Suggested change

	If your application is written in JavaScript as ESM, or compiled to ESM from TypeScript, then a loader hook is required to properly patch instrumentation.
	The custom hook for ESM instrumentation is `--experimental-loader=@opentelemetry/instrumentation/hook.mjs`.
	This flag must be passed to the `node` binary, which is often done as a startup command and/or in the `NODE_OPTIONS` environment variable.
	If your application is written in JavaScript as ESM, or compiled to ESM
	from TypeScript, a loader hook is required to patch instrumentation.
	The custom hook for ESM instrumentation is
	`--experimental-loader=@opentelemetry/instrumentation/hook.mjs`.
	This flag must be passed to the `node` binary, which is often done
	as a startup command or through the `NODE_OPTIONS` environment variable.

[theletterf]

Suggested change

	Much of OpenTelemetry JS documentation is written assuming the compiled application is run as CommonJS.
	The OpenTelemetry documentation assumes that the compiled application is run as CommonJS.

[theletterf]

Suggested change

	Much of OpenTelemetry JS documentation is written assuming the compiled application is run as CommonJS.
	The OpenTelemetry documentation assumes that the compiled application is run as CommonJS.

[theletterf]

Suggested change

	Much of OpenTelemetry JS documentation is written assuming the compiled application is run as CommonJS.
	The OpenTelemetry documentation assumes that the compiled application is run as CommonJS.

[theletterf]

Suggested change

	Much of OpenTelemetry JS documentation is written assuming the compiled application is run as CommonJS.
	The OpenTelemetry documentation assumes that the compiled application is run as CommonJS.

[theletterf]

Suggested change

	Much of OpenTelemetry JS documentation is written assuming the compiled application is run as CommonJS.
	The OpenTelemetry documentation assumes that the compiled application is run as CommonJS.

[JamieDanielson]

I've moved this back to draft for now! It will be easier when we can link to another doc.