Fix markdown-link-checker workflow (#542)

* Fix markdown-link-checker workflow

Added a configuration file that tells MLC to ignore the URLs in .github\workflows\mlc_config.json as MLC is falsely reporting these as dead

* Update markdown.yml

.github/workflows/markdown.yml

@@ -16,3 +16,4 @@ jobs:
     - uses: gaurav-nelson/github-action-markdown-link-check@v1
       with:
         use-quiet-mode: 'yes'
+        config-file: './.github/workflows/mlc_config.json'

.github/workflows/mlc_config.json

@@ -0,0 +1,14 @@
+{
+    "_comment": "Config for markdown-link-check. Resolves issue #540.",
+    "ignorePatterns": [
+      {
+        "pattern": "^https://github.com/RustScan/RustScan/workflows/Continuous%20integration/badge.svg"
+      },
+      {
+        "pattern": "^https://crates.io/crates/rustscan/"
+      },
+      {
+        "pattern": "^https://bees.substack.com/p/making-hacking-accessible"
+      }
+    ]
+  }