feat: add config file to retry on HTTP 429 status code (#1365)

* add config file to retry on 429 - HTTP 429 error is to wait to send another request

* set fallbackRetryDelay to 15s

* update config file to match workflow file name

.github/workflows/linkchecker.config.json

@@ -0,0 +1,5 @@
+{
+  "retryOn429": true,
+  "retryCount": 5,
+  "fallbackRetryDelay": "15s"
+}

.github/workflows/linkchecker.yml

@@ -1,5 +1,5 @@
 name: Check Markdown links
-on: 
+on:
   pull_request:
     paths: ["**.md"]
   push:
@@ -17,3 +17,4 @@ jobs:
         with:
           check-modified-files-only: "yes"
           base-branch: main
+          config-file: ".github/workflows/linkchecker.config.json"