Investigate linting for ERB templates

[jdudley1123]

See RFC 22

[jdudley1123]

This should be done as part of #153

[Floppy]

Assigning @pezholio this as it'll get done (or at least followed up) as part of his RFC in #153

[snim2]

I see there's a few of these!

• https://github.com/Shopify/erb-lint (also discussed in this blog post) and can use existing Rubocop configs
• https://github.com/github/erblint-github