Update the Build Procedure in README.md

As a first time contributor to the Conda-forge, the contributor would be reading the ``Build Procedure`` in ``Readme.md file,`` at first. Hence the steps that are to be taken to set the project in the local environment as well as ``to do lists`` before sending the PR should be mentioned clearly.

clear steps/tutorial links can be provided to let the contributor know how to get familiar with ``sphinx``. For example:
[sphinx Docs](https://www.sphinx-doc.org/en/master/usage/restructuredtext/index.html)

This can be followed by steps mentioned above. In addition before sending PR the contributor should check the changes made in src folder works well by verifying the docs file in their local directory.

(open command prompt=> ``sphinx-build . ../docs`` =>auto generated html file in docs folder can be found)

These steps are not mentioned below: