dependency update; require ucto >= 0.30

fixed wheel building for macos arm64: switched to Cirrus-CI

version bump for compilation against ucto v0.29

version bump for compilation against ucto v0.28

wheel building: install libxml2 in same prefix as the rest

dependency update: require ucto >= 0.26

ci, wheels: fix in musllinux wheel building

allow selecting another tag when building wheels

adapted for ucto v0.24.1 (breaks compatibility with older version)

removed python 2 example