Implement markdown and yaml linting, prepare eslint infrastructure

[dvonthenen]

This enables some linting/checks for Markdown, GH Action, YAML, and Shell Linting.

This introduces GitHub actions to check those things and allows users to check locally before submitting a PR. Running locally requires docker, but the user doesn't necessarily need to install or check manually before submitting a PR. To download all dependencies (ie make check = run all lints, checks), they can run make ensure-deps to download all dependencies, tools, and etc.

Addresses the following issues: #286 #285 #284

The updates to the Markdown are from the issues raised by the mdlint check.

If you don't feel this adds value to the project, feel free to close this PR and the issues as well.

[naomi-lgbt]

I love the idea of linting the code, but I'm not sure this approach is best for a JavaScript project?

We don't use shell, or go, or yaml.

And we should be linting the JS/TS with the eslint package (and prettier if we want to be extra robust). There's also a markdownlint-cli npm package we can use if we want to lint markdown.

[lukeocodes]

call me old fashioned but i have concerns about this tooling being part of my workflow.

there are so many lighter solutions inside the JS ecosystem that do not require docker to run :/

[dvonthenen]

Yup, I get it. It was the easiest lift without investing too much time (as in like 5mins). This isn't required for someone to open a PR as it will check in the GH action but uses the same mechanism for both. If this is too much for the project to add, you can close this PR.

[dvonthenen]

And we should be linting the JS/TS with the eslint package (and prettier if we want to be extra robust). There's also a markdownlint-cli npm package we can use if we want to lint markdown.

This doesn't tackle any JS linting.

[naomi-lgbt]

I hope you don't mind, but I didn't wanna just discard this entirely.

I pushed a commit to shift the runners into the JS ecosystem, and preserved the rules you configured. 💜

[dvonthenen]

Doesn't matter. It's your work and code.