Add 'What we learned with Clippy's feature freeze'

[blyxyas]

Post holding some information and a little retrospective on how the feature freeze went and what we as the Clippy team learned along the way. We also included some questions that I asked to Ada4a, our highlighted contributor in this feature freeze.

cc @ada4a @rust-lang/clippy

Rendered

[Kobzol]

Awesome work! Enjoyed both of your blog posts about this.

[ada4a]

Nice read, thanks again for the shout-out:)

[flip1995]

Really well written! Thanks for writing this up ❤️

If you, like me, wanted to learn the inner workings of the compiler and contribute
to it some day, but were intimidated by the development setup required for that, Clippy could be a nice stepping stone, as hacking on it doesn't require compiling rustc, but it interacts with a lot of compiler's data structures and APIs.

Hell yeah, that's what we're going for 🎉

[blyxyas]

Note for reviewers ⚠️ ⚠️

The date in the file is for tomorrow (22th of October) because I don't think we'll merge this in the 6 hours remaining. If the date in the file isn't that important and the CI workflows will take care of it, feel free to merge.

[Kobzol]

CI won't change the date, but also it's not super important, in the sense that we could just publish it with tomorrow's date (it is tomorrow somewhere on Earth already anyway 😆). I'll merge it tomorrow morning (EU time) if it doesn't get merged by then.

[Kobzol]

Oops, forgot yesterday, sorry.