Checking links in markdown files (#150)

.github/workflows/url-check-config.json

@@ -0,0 +1,7 @@
+{
+  "ignorePatterns": [
+    {
+      "pattern": "^(http|https)://crates.io/"
+    }
+  ]
+}

.github/workflows/url-check-on-change.yml

@@ -0,0 +1,18 @@
+name: Check Markdown links
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+
+jobs:
+  markdown-link-check:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - uses: gaurav-nelson/github-action-markdown-link-check@v1
+      with:
+        use-verbose-mode: 'yes'
+        use-quiet-mode: 'yes'
+        config-file: '.github/workflows/url-check-config.json'
+        check-modified-files-only: 'yes'

.github/workflows/url-check-periodic.yml

@@ -0,0 +1,17 @@
+name: Check Markdown links Periodically
+
+on:
+  schedule:
+  # Run everyday at 0:00 AM
+  - cron: "0 0 * * *"
+
+jobs:
+  markdown-link-check:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - uses: gaurav-nelson/github-action-markdown-link-check@v1
+      with:
+        use-verbose-mode: 'yes'
+        use-quiet-mode: 'yes'
+        config-file: '.github/workflows/url-check-config.json'

refactoring/index.md

@@ -2,11 +2,11 @@
 
 Refactoring is very important in relation to these topics. Just as important as the other topics covered here, is how to take good code and turn it into great code.
 
-We can use [design patterns](patterns/index.md) to DRY up code and generalize abstractions. We must avoid [anti-patterns](anti_patterns/index.md) while we do this. While they may be tempting to employ, their costs outweigh their benefits.
+We can use [design patterns](../patterns/index.md) to DRY up code and generalize abstractions. We must avoid [anti-patterns](../anti_patterns/index.md) while we do this. While they may be tempting to employ, their costs outweigh their benefits.
 
 > Shortcuts make for long days.
 
-We can also use [idioms](idioms/index.md) to structure our code in a way that is understandable. 
+We can also use [idioms](../idioms/index.md) to structure our code in a way that is understandable. 
 
 ## Tests