These files will be used by both the web and node versions of Puppeteer.
Another name for this might be "core" but I don't want to cause
confusion with the puppeteer-core package that we publish at the moment.
This is another step towards making Puppeteer agnostic of environment
and being able to run in Node or a browser.
The files in the `node` directory are ones that would only be needed in
the Node build - e.g. the code that downloads and launches a local
browser instance.
The long term vision here is to have three folders:
* node - Node only code
* web - Web only code
* common - code that is shared
But rather than do that in one PR I'm going to split it up to make it
easier to review and deal with.
Replacing the Node EventEmitter with Mitt caused more problems than
anticipated for end users due to the API differences and the amount of
people who relied on the EventEmitter API. In hindsight this clearly
should have been explored more and then released as a breaking v4.
This commit rolls us back to the built in Node EventEmitter library
which we can release to get everyone back on stable builds. We can then
consider our approach to migrating to Mitt and when we do do that we can
release it as a breaking change and properly document the migration
strategy and approach.
* chore: migrate to Mitt as the EventEmitter
This commit moves us to using Mitt [1] for the event emitter in
Puppeteer. This removes our dependency to Node's EventEmitter which is
part of a larger stream of work to enable a Puppeteer-web version that
doesn't depend on Node.
There are no large breaking changes as we support the main methods that
EventEmitter had, but it also provides some methods that Puppeteer
didn't use. Technically end users could depend on this but it's
unlikely.
[1]: https://github.com/developit/mitt
It conflicts with an inbuilt TypeScript `Request` type so can cause
confusion when in TS land. Note: `Response.ts` and `Worker.ts` also
suffer from this; PRs to rename them are incoming.
