Use commit message flag to control workflows

.github/workflows/ci.yml

@@ -12,6 +12,7 @@ on:
 
 jobs:
   ci:
+    if: "!contains(github.event.commits[0].message, '[ci skip]')"
     name: 'SUITE: ${{ matrix.test_suite }} / OS: ${{ matrix.os }}'
     runs-on: ${{ matrix.os }}
     strategy:

.github/workflows/third-party.yml

@@ -9,6 +9,7 @@ on:
       - master
 jobs:
   build_n_profile:
+    if: "!contains(github.event.commits[0].message, '[ci skip]')"
     runs-on: 'ubuntu-latest'
     steps:
     - name: Checkout Jekyll