Super linter

[prestoncarman]

Highlights from CHANGELOG.md

• Added a CI workflow to lint the code base

Issues Fixed

• Fixes #310

[ianfixes]

If all this linter accomplishes is to complain about the existing markdown style we're using (which is valid), I'd prefer not to add it. We already have a linter for the ruby code that allows a more nuanced configuration than this tool.

[prestoncarman]

A few notes:

• This linter actually runs many linters for a variety of languages. Each linter has its own configuration file which we can individually configure.
  • It may be that we want to alter the Markdown settings.
  • We could also pick to run only certain linters. For example, we could turn off Ruby or only turn on the C++ linter.
• The linter has been configured to only run on files that were changed in the PR.
• When I turned on the linter for the whole repo, it reported many errors. https://github.com/prestoncarman/arduino_ci/runs/4003931830?check_suite_focus=true Some of those may be related to the cpp/arduino/avr which we should ignore similar to #316.

Are there files it would be helpful to have a linter review? If so, I can configure the tool for those files. If not, then we can close this PR.

[ianfixes]

Don't get me wrong, I definitely like the idea of linting. I just find it weird to bring in an all-purpose linting tool ahead of any discussion about what problems we see & want to solve.

For example, the spell checker's utility was self-evident... there were a host of spelling errors, and if you had asked in advance whether the codebase had any then I probably would have doubted it.

Are there files it would be helpful to have a linter review?

I think it would be worthwhile to lint

• the YAML files for correctness (and I'm sure there are rules for things like the Norway bug).
• the Markdown files for a style that's aligned with what we already use (### Title instead of ** Title **, etc)
• C++ for whatever approximates the style currently in use. Hopefully it doesn't choke on all the macros.

I'd rather tackle that as 3 separate linters, since the "super linter" is going to be a bit inflexible as to individual linter versions being used concurrently.

[prestoncarman]

I have found the GitHub Action called Super-Linter easy to set up and configure. So instead of creating individual actions, I thought we could start with using this tool until it does not meet our needs. These are the individual linters that are being run to cover C++, Markdown, and YAML files.

• cpp-lint
• clang-format
• markdownlint
• YamlLint

This PR only includes linter configuration and any conflicting linting issues that need to be fixed. The linting configuration files for each language have been configured to allow the current code to pass all the tests. In the future, the configuration settings could be reviewed to see if any of those settings should be changed.