ci: pin github actions by hash and update via dependabot (#180)

* Add dependabot for github actions
* Pin all actions by hash

Author: xopham

.github/dependabot.yml

@@ -0,0 +1,15 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "monthly"
+    groups:
+      gh-actions-packages:
+        patterns:
+          - "*"

.github/workflows/codeql-analysis.yml

@@ -22,10 +22,10 @@ jobs:
         language: [ 'cpp' ]
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v2
+      uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2.7.0
 
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@v2
+      uses: github/codeql-action/init@b8d3b6e8af63cde30bdc382c0bc28114f4346c88 # v2.28.1
       with:
         languages: ${{ matrix.language }}
 
@@ -35,4 +35,4 @@ jobs:
         bin/cmake-build
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@v2
+      uses: github/codeql-action/analyze@b8d3b6e8af63cde30bdc382c0bc28114f4346c88 # v2.28.1