added workflow and correct the submodule path

Author: srdgame

.github/workflows/main.yml

@@ -0,0 +1,36 @@
+# This is a basic workflow to help you get started with Actions
+
+name: CI
+
+# Controls when the action will run. Triggers the workflow on push or pull request
+# events but only for the master branch
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+# A workflow run is made up of one or more jobs that can run sequentially or in parallel
+jobs:
+  # This workflow contains a single job called "build"
+  build:
+    # The type of runner that the job will run on
+    runs-on: ubuntu-latest
+
+    # Steps represent a sequence of tasks that will be executed as part of the job
+    steps:
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
+      - uses: actions/checkout@v2
+      
+      # Update submodules
+      - name: Submodules update
+        run: git submodule update --init --recursive
+
+      - uses: freeioe/freeioe_build_action@v1
+        with:
+          action: build_ext_all.sh
+
+      - uses: actions/upload-artifact@v2
+        with:
+          name: my-artifact
+          path: ${{ steps.build.outputs.filename }}

.gitmodules

@@ -1,3 +1,3 @@
 [submodule "snap7"]
 	path = snap7
-	url = git@github.com:srdgame/snap7.git
+	url = https://github.com/srdgame/snap7.git