Use a codespace and simplify the "getting started contributing" docs

[djmitche]

Let's make sure that GitHub codespaces can support building Taskwarrior, and then update the getting-started docs to suggest that approach, rather than installing the toolchains locally.

This will be a good issue to start with if you've used GitHub codespaces before and are familiar with how they are set up.

[ryneeverett]

I'm all for documenting codespaces but not sure why you'd want to make that the recommended development environment straightaway. Is local installation really so painful?

[djmitche]

We'll definitely keep the local installation instructions, but the trend is toward automated development environments and I suspect we'll get more casual code contributions if contributors can do it quickly and harmlessly in the browser. And, getting more people involved in hacking on Taskwarrior is pretty important to the health of the project!

[dathanb]

It seemed like a good learning opportunity, so I futzed around with it and just submitted #3144 to add the devcontainer / codespace config. If that looks good, I can contribute relevant instructions to the developer docs.

[hugginsio]

I presume these instructions should be added to doc/devel/contrib/development.md?

Would the following be sufficient:

• Brief explanation on creating a new Codespaces instance with a link to the GitHub docs.
• Callout that you can create a local devcontainer as well if you meet the system requirements, with a link to the Development Containers spec.

[djmitche]

Ideally this would be descriptive enough that someone new to GitHub codespaces could be up-and-running without reading a lot of docs from GitHub.

We want to enable easy drive-by contributions, so someone who knows either C++ or Rust, but not both, should see 3-4 simple steps to get up and building/testing Taskwarrior having modified code in the language they know.