[appveyor] Add Python 3.10 builds

Author: mpsonntag

appveyor.yml

@@ -17,6 +17,10 @@ environment:
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
       PYVER: 3
       BITS: 32
+    - PYTHON: "C:\\Python310"
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      PYVER: 3
+      BITS: 32
     - PYTHON: "C:\\Python36-x64"
       PYVER: 3
       BITS: 64
@@ -30,6 +34,10 @@ environment:
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
       PYVER: 3
       BITS: 64
+    - PYTHON: "C:\\Python310-x64"
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      PYVER: 3
+      BITS: 64
 
 init:
   - "ECHO %PYTHON% %vcvars% (%bits%)"