Adds resources for F20DV/F21DV

Adds the course page
https://f21dv.github.io/

And adds resources for D3.js, an open-source data visualization
JavaScript library

Year4.md

@@ -254,6 +254,11 @@ This is very brief, and should be followed by completing a further full Python o
 ## Data Visualisation and Analytics (F20DV/F21DV)
 [Course Details](https://www.hw.ac.uk/documents/pams/202122/F20DV_202122.pdf)
 
+- ### [F20DV/F21CV Course Page](https://f21dv.github.io/)
+
+- [D3.js Documentation](https://d3js.org/what-is-d3)
+- [Data Visualization Certification (D3.js) - freeCodeCamp Certification](https://www.freecodecamp.org/learn/data-visualization/)
+
 ---
 <div align="right">