add link checker (github#585)

* add link checker

* add config file

* continue on error

Co-authored-by: Lana Brindley <github@lanabrindley.com>

Author: jacobprall

.github/workflows/link-checker.yml

@@ -0,0 +1,13 @@
+name: Check Markdown links
+
+on: push
+
+jobs:
+  markdown-link-check:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - uses: gaurav-nelson/github-action-markdown-link-check@v1
+      with:
+        config-file: 'mlc_config.json'
+      continue-on-error: true

mlc_config.json

@@ -0,0 +1,13 @@
+{
+    "ignorePatterns": [
+        {
+            "pattern": "^/"
+        }
+    ],
+    "replacementPatterns": [
+        {
+            "pattern": ":currentVersion:",
+            "replacement": "latest"
+        }
+    ]
+}