Add: Commit checker to enforce 100 line length (#120)

Author: spnda

.github/workflows/docs-checker.yml

@@ -0,0 +1,24 @@
+name: Docs checker
+on:
+  pull_request:
+    branches:
+      - main
+    paths:
+      - 'docs/**'
+jobs:
+  validate-line-length:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      - name: Make sure git is installed
+        run: apt-get update && apt-get install git -y && git --version
+        # "https://google.com/serch"
+
+        # The first grep filters out everything that has a link in it. The second filters anything
+        # that is not an addition (prefixed by a single '+').
+      - name: Get changed file names of files changed in PR
+        run: git diff -U0 ${{ github.event.pull_request.base.sha }} ${{ github.sha }} | grep -P "^(?!.*(http|ftp|https):\/\/([\w_-]+(?:(?:\.[\w_-]+)+))([\w.,@?^=%&:\/~+#-]*[\w@?^=%&\/~+#-])).*" | grep -P "^\+{1}(?!\+)" > diff_files.txt
+      - name: Count line lengths in diff_files.txt
+        run: "awk -F: 'BEGIN { if(length>100) { err = 1; exit; } } END {exit err}' diff_files.txt"