Migrate to Webpack 5 and Upgrade Node.js to 20

[mmx900]

Context

• Fixes Update app to run on Node 18 or newer (NodeJS 16 has reached End of Support) #682
• To update Node.js, this PR migrates the project from Webpacker to Webpack 5 using jsbundling-rails. Initially, I also tried Shakapacker, but it seemed to require more effort. Since I am not an expert in Webpack (I primarily use importmap-rails at work), I may not be aware of all the considerations. However, if there is a compelling reason to use Shakapacker, I am open to retrying the migration.
• While tests are passing, we need to verify that the bundling works correctly on the production server and in other developers' dev environments.

Summary of Changes

• Following the jsbundling-rails guide, replaced Webpacker with Webpack and jsbundling-rails.
• Following the Webpack migration guide, upgraded Webpack to 5.
• Upgraded Node.js to 20.

Checklist

• Tested Mobile Responsiveness
• Added Unit Tests
• CI Passes
• Deploys to Heroku on test Correctly (Maintainers will handle)
• Added Documentation (Service and Code when required)

Screenshots

Before

After

[DeeDeeG]

Sorry for the delayed response, I will be unavailable to test this until at least the 15th, possible a few days after.

I can spin this up in Docker and see how that goes, and ideally (pay for and run it in) a test Dyno on Heroku.

Thank you for the multiple contributions!

[mmx900]

I’m wondering if I could help test this PR.
It looks like there’s a staging server—would it be possible to deploy this branch there and check the logs?
I tried clicking “View logs” at https://github.com/RefugeRestrooms/refugerestrooms/deployments, and it seems to redirect to Heroku, but I don’t have access.

I’m also open to deploying to a Heroku Dyno myself, but since I’m new to Heroku, I wanted to check first if there’s an easier or preferred way.

[DeeDeeG]

I don't think I can keep maintaining this project "by myself" (de-facto, and for lack of a way to reach the other maintainers to confirm whether help is on the way or not). See: #686 (comment)

Sorry about that.

EDIT to clarify: I don't intend to try and move this or any other PR's forward at this time. I'm retiring from the project. I was already effectively retired, but I left open some hope of the ambiguity of the situation resolving in a positive direction. I don't often hear back from the other maintainers, I don't have the skills by myself. I should simply step away, but I had to come back and say I'm retiring or no-one would know if I am still reviewing PR's or not. So, yeah. I'm retiring from this project. Sorry again.

EDIT 2: Feel free to ping me for information or if I am needed for something along those lines. But I'm not reviewing any new features or fixes. I can't confidently push them to prod anymore, so there would be no benefit to merging them here on GitHub with no way to make it into production.