Add linkcheck

.github/workflows/link_check.yml

@@ -0,0 +1,39 @@
+name: Check Links
+
+on:
+  pull_request:
+    branches:
+      - main
+  push:
+    branches:
+      - main
+  schedule:
+    - cron: '0 5 * * *'
+  workflow_dispatch:
+
+jobs:
+  markdown-link-check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Check links in Markdown files
+        uses: gaurav-nelson/github-action-markdown-link-check@v1
+
+  notebook-link-check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Set up Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: '3.x'
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -U pytest pytest-check-links langsmith langchain GitPython
+      - name: Check links in notebooks
+        env:
+          LANGCHAIN_API_KEY: test
+        run: pytest -o python_files=non_python_only --check-links --ignore="*.py" -k .ipynb --check-links-ignore "https://(api|web)\.smith\.langchain\.com/.*" .