add universal2 wheels for python 3.8

Author: Jeff Whitaker

.github/workflows/build-wheels.yml

@@ -46,6 +46,9 @@ jobs:
           - python-version: "3.10"
             os: ubuntu-latest
             platform: aarch64
+          - python-version: "3.8"
+            os: macos-10.15
+            platform: x86_64
           - python-version: "3.9"
             os: macos-10.15
             platform: x86_64