Webpack: Reqire process.js for polyfills

[noahtallen]

Changes proposed in this Pull Request

In #54793, a dependency is introduced on lib0. This causes our webpack build to fail with the following error:

ERROR in ../node_modules/lib0/environment.js 14:29-36
Module not found: Error: Can't resolve 'process/browser' in '/home/nt/source/wp-calypso/node_modules/lib0'
Did you mean 'browser.js'?
BREAKING CHANGE: The request 'process/browser' failed to resolve only because it was resolved as fully specified
(probably because the origin is strict EcmaScript Module, e. g. a module with javascript mimetype, a '*.mjs' file, or a '*.js' file where the package.json contains '"type": "module"').
The extension in the request is mandatory for it to be fully specified.
Add the extension to the request.
resolve 'process/browser' in '/home/nt/source/wp-calypso/node_modules/lib0'
  Parsed request is a module
  using description file: /home/nt/source/wp-calypso/node_modules/lib0/package.json (relative path: .)
    Field 'browser' doesn't contain a valid alias configuration
    resolve as module
      /home/nt/source/wp-calypso/node_modules/lib0/node_modules doesn't exist or is not a directory
      /home/nt/source/wp-calypso/node_modules/node_modules doesn't exist or is not a directory
      looking for modules in /home/nt/source/wp-calypso/node_modules
        existing directory /home/nt/source/wp-calypso/node_modules/process
          using description file: /home/nt/source/wp-calypso/node_modules/process/package.json (relative path: .)
            using description file: /home/nt/source/wp-calypso/node_modules/process/package.json (relative path: ./browser)
              Field 'browser' doesn't contain a valid alias configuration
              /home/nt/source/wp-calypso/node_modules/process/browser doesn't exist
      /home/nt/source/node_modules doesn't exist or is not a directory
      looking for modules in /home/nt/node_modules
        /home/nt/node_modules/process doesn't exist
      /home/node_modules doesn't exist or is not a directory
      /node_modules doesn't exist or is not a directory
 @ ../node_modules/lib0/buffer.js 8:0-39 77:24-37 80:26-39
 @ ../node_modules/yjs/dist/yjs.mjs 8:0-38 715:11-32
 @ ../node_modules/@automattic/isolated-block-editor/build-module/components/block-editor-contents/use-yjs/yjs-doc.js 1:0-27 13:18-25 38:24-45 101:32-55 116:10-25 121:10-25

Based on some investigation, this happens when webpack tries to alias the process variable in lib0/environment.js. Based on the error The extension in the request is mandatory for it to be fully specified, I changed process/browser polyfill to process/browser.js in our webpack config. This fixed the error in the React 17 PR.

Also, according to https://stackoverflow.com/a/65018686, it's helpful to add a dependency on process (though I'm not sure if this is needed), and we don't have to add the alias if we use ProvidePlugin.

Testing instructions

CI should pass. Also try yarn start locally.

[github-actions]

Link to Calypso live: https://calypso.live?image=registry.a8c.com/calypso/app:build-14091
Link to Jetpack Cloud live: https://calypso.live?image=registry.a8c.com/calypso/app:build-14091&env=jetpack

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.

[fullofcaffeine]

CI tests pass, yarn start works fine starting Calypso without errors. After assets were compiled, I smoke tested Calypso and it looks fine 👍🏻