Version 1.1 for Rocq 9.0.1

This release updates to Rocq 9.0. Besides this, there are two new contributions, from @dominik-kirst in collaboration with two new contributors:

• @Janis-Bai contributes a mechanisation of Hilbert systems for FO (proven equivalent to ND), and a mechanisation of Gödel's first incompleteness theorem and Tarski's theorem via Carnap's diagonal lemma. (in #8)
• @HaoyiZeng contributes the BDP paper mechanization (in #9)

These improvements are significant enough to bump the version number, making this version 1.1.

Thanks a lot to all involved 🎉