ci(github): add Windows testing using Actions

.github/workflows/kitchen.yml

+---
+name: CI
+
+'on': [push, pull_request]
+
+env:
+  machine_user: kitchen
+  machine_pass: Pass@word1
+  machine_port: 5985
+  KITCHEN_LOCAL_YAML: kitchen.github.yml
+
+jobs:
+  build:
+    runs-on: windows-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/cache@v1
+        with:
+          path: vendor/bundle
+          key: ${{ runner.os }}-gems-${{ hashFiles('**/Gemfile.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-gems-
+      - shell: powershell
+        run: |
+          $password = ConvertTo-SecureString $env:machine_pass -AsPlainText -Force
+          New-LocalUser $env:machine_user -Password $password
+          Add-LocalGroupMember -Group "Administrators" -Member $env:machine_user
+      - shell: powershell
+        run: >
+          Set-WSManQuickConfig -Force;
+          Set-WSManInstance -ResourceURI winrm/config/service
+          -ValueSet @{AllowUnencrypted="true"}
+      - run: gem install bundler --quiet --no-document
+      - name: Bundle install
+        run: |
+          bundle config path vendor/bundle
+          bundle install --jobs 4 --retry 3
+      - run: bundle exec kitchen test

kitchen.github.yml

+---
+driver:
+  name: proxy
+  host: localhost
+  reset_command: "exit 0"
+  port: 5985
+  username: kitchen
+  password: Pass@word1
+
+platforms:
+  - name: windows
+
+provisioner:
+  salt_install: bootstrap
+  salt_bootstrap_options: -pythonVersion 3 -version 3000.3
+  init_environment: >
+    C:\salt\salt-call --local state.single file.managed
+    C:\Users\kitchen\AppData\Local\Temp\kitchen\srv\salt\win\repo-ng\salt-minion-py3.sls
+    source=https://github.com/saltstack/salt-winrepo-ng/raw/master/salt-minion-py3.sls
+    skip_verify=True makedirs=True
+
+suites:
+  - name: v3000-py3
+    provisioner:
+      state_top:
+        base:
+          '*':
+            - salt.minion
+      pillars:
+        top.sls:
+          base:
+            '*':
+              - salt
+              - v3000-py3
+      pillars_from_files:
+        salt.sls: test/salt/pillar/salt.sls
+        v3000-py3.sls: test/salt/pillar/v3000-py3.sls
+    verifier:
+      inspec_tests:
+        - path: test/integration/v3000-py3