denote grade free zone, closes #17

Author: brownsarahm

activities/practice.md

@@ -11,6 +11,11 @@ kernelspec:
   name: python3
 ---
 
+```{important}
+The grade free zone covers classes 1-5, ending on 2022-09-21.
+```
+
+
 # More Practice
 
 ```{note}

activities/prepare.md

@@ -11,6 +11,11 @@ kernelspec:
   name: python3
 ---
 
+```{important}
+The grade free zone covers classes 1-5, ending on 2022-09-21.
+```
+
+
 # Prepare for the next class
 
 ```{warning}

activities/review.md

@@ -11,6 +11,10 @@ kernelspec:
   name: python3
 ---
 
+```{important}
+The grade free zone covers classes 1-5, ending on 2022-09-21.
+```
+
 
 # Review