CI workflow to ignore markdown changes (#641)

Ignore markdown and docs folder changes in CI triggers.

Author: JeffFessler

.github/workflows/CI.yml

@@ -1,10 +1,17 @@
 name: CI
 on:
   pull_request:
+    paths-ignore:
+      - '**.md'
+      - 'docs/**'
   push:
     branches:
       - master
+    paths-ignore:
+      - '**.md'
+      - 'docs/**'
     tags: '*'
+
 jobs:
   test:
     name: Julia ${{ matrix.version }} - ${{ matrix.os }} - ${{ matrix.arch }} - ${{ github.event_name }}