Feature/verify (#30)

* * verify connection

* * use git clone for SSH connection test

* rerun CI

* rerun CI

* * rename verification

* * add badge

* * cross-platform verification

* * remove known_hosts for test

* Revert "* remove known_hosts for test"

This reverts commit 96f512a3a1.

.github/workflows/verify.yml

@@ -0,0 +1,25 @@
+# https://help.github.com/en/articles/workflow-syntax-for-github-actions
+
+on: "pull_request"
+name: Connection test
+jobs:
+  ssh:
+    name: Connect to github.com on ${{ matrix.platform }}
+    runs-on: ${{ matrix.platform }}
+    strategy:
+      matrix:
+        platform:
+        - "Windows-latest"
+        - "macOS-latest"
+        - "Ubuntu-latest"
+      fail-fast: false
+    steps:
+    - name: Install SSH key
+      uses: shimataro/ssh-key-action@development
+      with:
+        private-key: ${{ secrets.SSH_KEY }}
+        public-key: ${{ secrets.SSH_KEY_PUBLIC }}
+        name: 'id_rsa' # optional
+        known-hosts: ${{ secrets.KNOWN_HOSTS }} # optional
+    - name: git clone through SSH
+      run: git clone git@github.com:shimataro/ssh-key-action.git tmp