Allow hard-coded "sheet" URL to be passed at build time

[avengerpenguin]

This PR changes a few small things so I'd happily take some feedback and chat about whether they are all a net good for the project. I've done them for myself, but perhaps it improves things for others too.

In summary:

1. The webpack build allows env vars (e.g. from Docker build args) to set the sheet ID (URL) and name at build time

2. The code itself is refactored a little to allow dependency-injection of the sheet URL

3. The Dockerfile does the webpack build etc. at build time

4. The Docker build is now multistage which makes it simpler

Rationale

I liked the idea of being able to run the project as it is while also being able to run a build, even from my own Dockerfile elsewhere, that spits out an HTML file that is pre-baked with the radar data. This would allow deploying it as part of a wider static site, e.g. on Github pages.

It seems a reasonable code architecture to hoist out mentions of window to the top-level file and inject that info in such that all JS files from factory.js are abstracted away from the fact that info came from a query string.

Docker Build Changes

The Docker container running the bulk of the build as a CMD on start seemed odd when -- as far as I can see -- the build output is entirely a function of source files alone.

Maybe there's more flexibility intended around being able to swap out env vars without having to rebuild the container?

I technically do not need the changes for the sheet URL injection, but I'd have to add something to pass the build args into the environment at container runtime.

Small Tweaks

Some stuff I noticed along the way:

1. There's two webpack configs but they're very close so I hoisted up the entry part to the common file. There may be a reason it is the way it is.

2. I kept finding it odd to have lots of references to "sheet" and "Google Sheet Input" throughout when it's clearly been extended to allow generic JSON and CSV outside of Google sheets. I suspect this is historic but I changed the name of the top export from factory in the hope this is a positive change in the right direction. I can revert if needed though.

3. For JSON and CSV input, the h1 title just uses the file name. Since we can now inject I've allowed a SHEET_NAME to be set at build time to override that behaviour.

Tests

I've checked no tests fail, but not added any since the JS changes are meant to be a refactor but perhaps this change warrants an e2e test to verify the new functionality made available.

[devansh-sharma-tw]

Hi @avengerpenguin ,

Thanks for raising this PR!
Sorry for the delay in responding back. We are currently in discussion with the team regarding this PR and will update here shortly.

Thanks!