Added VS2022 job and C++20 and C++latest jobs to AppVeyor CI.

Author: Lastique

appveyor.yml

@@ -1,5 +1,5 @@
 # Copyright 2016, 2017 Peter Dimov
-# Copyright 2019 - 2021 Andrey Semashev
+# Copyright 2019-2022 Andrey Semashev
 # Distributed under the Boost Software License, Version 1.0.
 # (See accompanying file LICENSE_1_0.txt or copy at http://boost.org/LICENSE_1_0.txt)
 
@@ -23,22 +23,27 @@ environment:
       EXTRA_TESTS: 1
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
     - TOOLSET: msvc-14.1
-      CXXSTD: 14,17
+      CXXSTD: 14,17,latest
       ADDRMD: 32,64
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
     - TOOLSET: msvc-14.2
       ADDRMD: 32,64
-      CXXSTD: 14,17
+      CXXSTD: 14,17,20,latest
       THREADING: single,multi
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+    - TOOLSET: msvc-14.3
+      ADDRMD: 32,64
+      CXXSTD: 14,17,20,latest
+      THREADING: single,multi
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
     - TOOLSET: clang-win
       ADDRMD: 32
-      CXXSTD: 14,17
+      CXXSTD: 14,17,latest
       ENV_SCRIPT: C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars32.bat
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
     - TOOLSET: clang-win
       ADDRMD: 64
-      CXXSTD: 14,17
+      CXXSTD: 14,17,latest
       ENV_SCRIPT: C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
     - TOOLSET: gcc