Add config.cache example to webpack.local-config.js note

[kazarmy]

This pr adds a config.cache example to the webpack.local-config.js note in CONTRIBUTING.md, and so now both parameters are being used. This is probably the last change that I want to make to the note.

---

Some side notes:

• I profiled the uncached webpack build, terminating the server with the code below. It seems that babel transformations take up a large chunk of the time.

module.exports = function (config, serverConfig) {
  serverConfig.setupMiddlewares = (middlewares, _devServer) => {
    let attachedOpen = false;
    for (const m of middlewares) {
      if (m.name === 'webpack-dev-middleware' && !attachedOpen) {
        m.middleware.waitUntilValid(() => {
          process.kill(process.pid, 'SIGINT');
        });
        attachedOpen = true;
      }
    }
    return middlewares;
  };
};

• With the (cached) build at sub-10 seconds, I had a better user experience with opening the browser tab in parallel with the build, rather than opening it after the build.

[codecov]

Codecov Report

Base: 88.55% // Head: 88.55% // No change to project coverage 👍

Coverage data is based on head (97f8244) compared to base (b5b2ec2).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4446   +/-   ##
=======================================
  Coverage   88.55%   88.55%           
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  Files         283      283           
  Lines       25533    25533           
  Branches     6879     6879           
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  Hits        22611    22611           
  Misses       2715     2715           
  Partials      207      207           

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[julienw]

Thanks! Usually I keep the webpack server running in background all the time, so I don't get this first-build penalty often. It's also why I usually don't use this behavior of opening a tab automatically.

Maybe one day we'll switch to some other tooling such as vite that's faster and has a working HMR setup...

[julienw]

Mmm I wonder if we should have this by default in our config actually. It looks like I considered doing this because I have an open tab on this configuration.
It would be good to get your feedback after a few days using this.

[kazarmy]

I currently do plan to find out whether server config changes force a full rebuild, but what is next isn't yet set in stone.

[kazarmy]

Modifying serverConfig.static roughly triples the cached webpack build time lol

[julienw]

thx!

[kazarmy]

Usually I keep the webpack server running in background all the time, so I don't get this first-build penalty often.

I can't justify leaving my laptop on power and unattended, and hibernating it isn't 100% reliable.