Write a "How to write your own Hegel library" article #3
Description
Should fit under how-to/write-your-own-library.md and be linked on the How to section of the front page.
We should mention Hegelator, conformance tests, and common pitfalls we ran into while implementing Hegel libraries. We should aim to either make this page the source of truth on writing a new Hegel library, or link out to those sources of truth, such that pointing someone to this page gives them all the context they need to do a good job writing a new library.