platform identifiers don't account for arm64

[ddelange]

both the dependency speficier recommendation in the isal README, and the dependency specifier in xopen pyproject.toml, do not account for new macs:

>>> from packaging.markers import default_environment
>>> default_environment()
{
    'implementation_name': 'cpython',
    'implementation_version': '3.12.8',
    'os_name': 'posix',
    'platform_machine': 'arm64',
    'platform_release': '24.6.0',
    'platform_system': 'Darwin',
    'platform_version': 'Darwin Kernel Version 24.6.0: Mon Jul 14 11:30:40 PDT 2025; root:xnu-11417.140.69~1/RELEASE_ARM64_T6041',
    'python_full_version': '3.12.8',
    'platform_python_implementation': 'CPython',
    'python_version': '3.12',
    'sys_platform': 'darwin'
}

hence it does not install isal with xopen:

$ pip install xopen
Collecting xopen
  Downloading xopen-2.0.2-py3-none-any.whl.metadata (15 kB)
Downloading xopen-2.0.2-py3-none-any.whl (17 kB)
Installing collected packages: xopen
Successfully installed xopen-2.0.2
$ pip install isal
Collecting isal
  Downloading isal-1.8.0-cp312-cp312-macosx_11_0_arm64.whl.metadata (10 kB)
Downloading isal-1.8.0-cp312-cp312-macosx_11_0_arm64.whl (189 kB)
Installing collected packages: isal
Successfully installed isal-1.8.0

[ddelange]

why do you add/recommend the platform specifiers in the first place? better to let pip attempt a source install instead? and fix the sdist or add wheels if users run into problems?