Added README

The details regarding dependency and usage is provided in the README file.

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>
Use ndk-build present in NDK folder

Do not expect it to be in your PATH. Use the path provided by the user. This
mistake has been repeated. Do not repeat it again.

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>