Add Legend for Patients by Nationality graph

Created by: KaustubhDamania

Describe the bug There should be a legend for the 'Patients by Nationality' graph since in the pic below, one has to hover and check for the nationalities.

The legend could be added similar to the pic below:

To Reproduce Steps to reproduce the behavior:

1. Go to https://www.covid19india.org/deepdive
2. Scroll down to 'Patients by Nationality' graph

Expected behavior There should have been a legend for that specific graph.

Desktop (please complete the following information):

• OS: Ubuntu 18.04
• Browser: Firefox
• Version: 74

Additional context I would like to work on this issue.