Add dockerfile for cli

[coolreader18]

Description of Changes

This just curls & runs the install script on a blank image. Technically won't work until the new script is up on the website.

Expected complexity level and risk

1

Testing

I've tested a little bit and will test more once this is merged and I can download the artifacts built from CI (my system has too new a glibc version 😢 )

[gefjon]

I would expect that we want to have other things also present inside this docker. E.g.:

• Rustup, cargo, rustc, the wasm32-unknown-unknown target, and everything else one needs to compile and publish a Rust module.
• Dotnet, the dotnet WASI SDK, and whatever else one needs to compile and publish a C# module.
• wasm-opt.

Testing I would expect to be done:

• One can spacetime start using the docker and connect an external client (e.g. a web browser) to the running host.
• One can bind-mount a module project directory into the docker and then spacetime publish it, both locally and to a remote host.
• One can use spacetime call and spacetime sql from the docker, both locally and to a remote host.

~~Bonus points:

• One can bind-mount a Rust, C# or TypeScript client project directory into the docker and then compile and run it, connecting to either a local or a remote host.~~

Nope. We're sticking to having this be for module-side dev and whatnot. People building clients can do so on their own.

[coolreader18]

I'll test this further once this is merged and I can download the artifacts built from CI on master (my system has too new a glibc version 😢)