docs: note about musllinux mess

See #934.

README.md

@@ -25,14 +25,15 @@ What does it do?
 |   | macOS Intel | macOS Apple Silicon | Windows 64bit | Windows 32bit | Windows Arm64 | manylinux<br/>musllinux x86_64 | manylinux<br/>musllinux i686 | manylinux<br/>musllinux aarch64 | manylinux<br/>musllinux ppc64le | manylinux<br/>musllinux s390x |
 |---------------|----|-----|-----|-----|-----|----|-----|----|-----|-----|
 | CPython 3.6   | ✅ | N/A | ✅  | ✅  | N/A | ✅  | ✅  | ✅ | ✅  | ✅  |
-| CPython 3.7   | ✅ | N/A | ✅  | ✅  | N/A | ✅ |✅  | ✅ | ✅  | ✅  |
-| CPython 3.8   | ✅ | ✅  | ✅  | ✅   | N/A | ✅ | ✅  | ✅ | ✅  | ✅  |
-| CPython 3.9   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  |
+| CPython 3.7   | ✅ | N/A | ✅  | ✅  | N/A | ✅ | ✅  | ✅ | ✅  | ✅  |
+| CPython 3.8   | ✅ | ✅  | ✅  | ✅  | N/A | ✅ | ✅  | ✅ | ✅  | ✅  |
+| CPython 3.9   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅³ | ✅ | ✅ | ✅  | ✅  |
 | CPython 3.10  | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  |
 | PyPy 3.7 v7.3 | ✅ | N/A | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A |
 
 <sup>¹ PyPy is only supported for manylinux wheels.</sup><br>
 <sup>² Windows arm64 support is experimental.</sup><br>
+<sup>³ Alpine 3.14 and 3.15's default python3 [currently cannot load](https://github.com/pypa/cibuildwheel/issues/934) musllinux wheels.</sup><br>
 
 - Builds manylinux, musllinux, macOS 10.9+, and Windows wheels for CPython and PyPy
 - Works on GitHub Actions, Azure Pipelines, Travis CI, AppVeyor, CircleCI, and GitLab CI