add sphinx-tags to gh workflows

Author: mikofski

.github/workflows/build-gh-pages.yml

@@ -21,6 +21,7 @@ jobs:
     - name: Install dependencies
       run: |
         pip install jupyter-book
+        pip install sphinx-tags
 
     - name: Build the book
       run: |

.github/workflows/preview.yml

@@ -26,6 +26,7 @@ jobs:
     - name: Install dependencies
       run: |
         pip install jupyter-book
+        pip install sphinx-tags
 
     - name: Build the book
       run: |

requirements.txt

@@ -0,0 +1,2 @@
+jupyter-book
+sphinx-tags