Update event names in README.md to match code

[frenzzy]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

Docs and code uses different even names, see:
https://github.com/webpack-contrib/webpack-serve/blob/v1.0.2/index.js#L42-L48

Breaking Changes

Additional Info

[shellscape]

Thanks 🍺

[frenzzy]

Btw, why do you convert stats to json here?
https://github.com/webpack-contrib/webpack-serve/blob/v1.0.2/index.js#L41

...
const json = stats.toJson();
if (stats.hasErrors()) {
  bus.emit('compiler-error', { json, compiler: comp });
}
...

Why not just pass the whole status object to compiler-* events?
Users may want to take only specific info in such cases, for example:

stats.toString({ all: false, errors: true, warnings: true, moduleTrace: true })

Using stats.toString() without arguments probably much slower because all possible info will be captured, if I understood correctly.