Publish PDF version of RTD documentation

[arijitde92]

Fixes #125

I have added pdf and epub options in the .readthedocs.yaml file and have tested the documentation in readthedocs. The pdf and epub versions of the documentation can now be downloaded. As per the screenshot below, the option to download pdf version is shown in the red rectangle.

After clicking on the above link, the pdf document appears in a browser tab as shown below-

This fixes issue #125

Let me know if any other changes are required in this PR.

Tasks

• [x] PR is descriptively titled 📑 and links the original issue above 🔗
• [x] Tests pass -- look for a green checkbox ✔️ a few minutes after opening your PR Run tests locally to check for errors.
• [x] Commits are in uniquely-named feature branch and has no merge conflicts 📁

Signed-off-by: Arijit De arijitde2050@gmail.com

[arijitde92]

Sign off issue. Will raise another PR