feat: Various improvements for electron/template

[felixrieseberg]

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.
• The changes are appropriately documented (if applicable).
• The changes have sufficient test coverage (if applicable).
• The testsuite passes successfully on my local machine (if applicable).

Summarize your changes:

1. Updated the core .gitignore file to cover most common Node.js tools, ensuring that nobody gets caught by surprise check-in files
2. Added a README for the webpack template. It's currently the same as for electron/template, but maybe that's okay?
3. Documented renderer.js a little bit, explaining what's what
4. Made the index.html a bit prettier 😉

[malept]

Ah, the Node.gitignore...

🤔 it'd be interesting if this were automatically updated with a GitHub Action...

[malept]

I don't know whether this fits in the Webpack template.

[malept]

Let's just keep this in electron/template only for now.

[malept]

I wonder if this should go in a separate CSS file, mostly to show that non-transpiled files work fine with Forge+Webpack. There was a question about it in the issue tracker the other day.

[felixrieseberg]

Sure, sure - I'd say let's incrementally improve this as much as there's time and appetite! If you think this is better than what's there right now, let's go with this first - I'm just trying to get electron/template 🚢