Setup SwiftLint

[stackotter]

Linting is a great way of ensuring that a repository's code is neat. Setting up SwiftLint consists of two steps:

• Create the SwiftLint configuration file and decide which rules to use
• Create a GitHub action to automatically run SwiftLint

[ajstrand]

Do you have an idea of which rules you'd like to support?

From looking at swift lint it seems like there are quite a lot.

[stackotter]

I've setup a basic configuration now (on the dev branch). Many of the good SwiftLint rules are just enabled by default, so it's pretty close to a default configuration, just with a few changes (such as ignoring files generated by gyb). I've set up a simple GitHub Action for it too 👍