github workflow: Support windows-2022

The provided host for windows-latest is migrating across from
windows-2019 to windows-2022 on github.  This allows things to be built on
a windows-2022 system.

.github/workflows/main.yml

@@ -112,7 +112,7 @@ jobs:
         run: |
           make -C examples/${{matrix.OS}}
   ms-build:
-    runs-on: windows-latest
+    runs-on: windows-2022
 
     steps:
       - uses: actions/checkout@v2