New feature : linting

[ericproulx]

This PR adds a linting feature that can activated through Grape.config.lint = true or lint! in a Grape::Api.
Suggested in this comment.

By design, Grape's CI has Grape.config.lint = true, so all specs calling an endpoint are linted.

[grape-bot]

	1 Warning
⚠️	Unless you're refactoring existing code or improving documentation, please update CHANGELOG.md.

Here's an example of a CHANGELOG.md entry:

* [#2557](https://github.com/ruby-grape/grape/pull/2557): New feature : linting - [@ericproulx](https://github.com/ericproulx).

Generated by 🚫 Danger

[dblock]

Should we call it lint! since it's Rack::Lint?

But thinking about it, maybe we need something more generic that allows one to inject middleware here, including potentially the ability to remove Rack::Head?

[ericproulx]

Should we call it lint! since it's Rack::Lint?

But thinking about it, maybe we need something more generic that allows one to inject middleware here, including potentially the ability to remove Rack::Head?

The middleware stack lacks a delete function. I think we should do something like ActionDispatch::MiddlewareStack

[dblock]

Please document this in the README if you want it merged.

That said, also consider not merging this and doing a configurable middleware implementation instead.