ci(workflow): run script in headless mode on VMs (#643)

Run script in headless mode on all supported distributions, on Digital Ocean VMs, with GitHub Actions

.github/workflows/lint.yml

@@ -0,0 +1,26 @@
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
+
+name: Lint
+jobs:
+  shellcheck:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - name: shellcheck
+      uses: ludeeus/action-shellcheck@0.0.1
+      with:
+        args: openvpn-install.sh -e SC1091,SC2164,SC2034,SC1072,SC1073,SC1009
+  shfmt:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - name: shfmt
+      uses: bltavares/actions/shfmt@master
+      env:
+        SHFMT_ARGS: -d