Add steps to build documentation in Readme
Though it's already mentioned in the documentation footer that it's built using Sphinx. It would be good if we document the build steps in the Readme.
- It will be particularly helpful for first time users starting to work on documentation.
- Avoid any inconsistencies in build e.g. I got this issue
sphinx_rtd_theme is no longer a hard dependency since version 1.4.0. Please install it manually.(pip install sphinx_rtd_theme)
- Since this is a long documentation we can add a live-reload tool like sphinx-autobuild that will support live edits while previewing the doc