Chapar 8.11.0 maintenance release

Maintenance release with Coq 8.11 compatibility, featuring the following changes:

Fixed

• Compatibility with Coq 8.11
• Ignore more untracked files such as .vos
• Remove mention of extracted OPAM package in README.md

Changed

• Add Proof using annotations for faster .vos/.vio compilation
• Ignore undeclared scope warning