1.28.0

Updates:

• ⚠️ Drop support for Python 3.5 and 3.6
• C extension reworked to be compatible with the Python Stable ABI. Rather than generating per-python-version wheels, simplified deploy to only produce abi3 wheels.
• Add usedforsecurity flag to all hashlib calls to satisfy FIPS audits (#219)
• Fix missing py.typed from installed package. #207, #241
• Fix comparison of default UDP assignment with API-provided object. #213
• Add __hash__ method for UserEnumMemberContainer. #239
• Fix use of enums in concatenation expressions. #230
• Fix an amusing edge-case that causes an out-of-memory crash. #224