Add explicit events dependency

[alxndrsn]

TODO

• add a test which fails against existing codebase similar to how linked issues fail, and passes with the updates in this PR
• add a test for node-js builds to show that import 'pouchdb-events' === import 'node:events'

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This seems to be a common issue:

• Dynamic require of "events" is not supported #8968
• pouchdb-utils depends on events npm package for the browser build, but does not declare it as a dependency. #8985
• Using pouchdb-browser (+ pouchdb-adapter-memory) expects nodeJS APIs #8989
• Support observable for easy integration in sveltekit/react/vuejs/… #9072
• new PouchDb. TypeError: The superclass is not a constructor. #9078

I think it was introduced by 404346b, which upgrade from webpack 1 to webpack 5. From the webpack docs:

Webpack 5 no longer polyfills Node.js core modules automatically which means if you use them in your code running in browsers or alike, you will have to install compatible modules from npm and include them yourself.

• https://webpack.js.org/configuration/resolve/

Alternatively, it may come from rollup.

Hopefully:

Closes #8968
Closes #8985
Closes #8989
Closes #9072
Closes #9078

[alxndrsn]

Less convinced now:

PR has been updated to handle events dependency like other browser-specific polyfills via new pouchdb-events package.

> e1 = require('node:events'); e2 = require('./node_modules/events');
<ref *1> [Function: EventEmitter] {
  once: [Function: once],
  EventEmitter: [Circular *1],
  defaultMaxListeners: [Getter/Setter],
  init: [Function (anonymous)],
  listenerCount: [Function (anonymous)]
}
> e1
<ref *1> [Function: EventEmitter] {
  addAbortListener: [Function: addAbortListener],
  once: [AsyncFunction: once],
  on: [Function: on],
  getEventListeners: [Function: getEventListeners],
  getMaxListeners: [Function: getMaxListeners],
  EventEmitter: [Circular *1],
  usingDomains: true,
  captureRejectionSymbol: Symbol(nodejs.rejection),
  captureRejections: [Getter/Setter],
  EventEmitterAsyncResource: [Getter],
  errorMonitor: Symbol(events.errorMonitor),
  defaultMaxListeners: [Getter/Setter],
  setMaxListeners: [Function (anonymous)],
  init: [Function (anonymous)],
  listenerCount: [Function (anonymous)]
}
> e2
<ref *1> [Function: EventEmitter] {
  once: [Function: once],
  EventEmitter: [Circular *1],
  defaultMaxListeners: [Getter/Setter],
  init: [Function (anonymous)],
  listenerCount: [Function (anonymous)]
}
> e1.EventEmitter === e2.EventEmitter
false