Update Dockerfile to modern syntax and include dependencies

[wgibbs-rs]

I found that using Docker was a pain on Debian Linux, as it had no documentation and did not already include the required files, like the Rust toolchain, curl, and build tools.

I've updated the Dockerfile to both use modern Docker syntax ( ENV key=var ) and to automatically install the Rust toolchain, curl (required for Rust), and the build-essentials needed for CC to work.

I also updated the CHANGELOG.md file to include these changes.

I've tested this on my machine, and found no issues (besides taking a while on the first build).

Let me know if there's anything else I need to do!

[wgibbs-rs]

Hold on- I'm trying to fix the Github Actions runner, as it will need an update with the new Dockerfile.

[wgibbs-rs]

nevermind.... I'll be back!