Add documentation about `hello world!` jarvil program in `README.rst`

[gabhijit]

Currently, one is able to do basic cargo build. In order to get started, it's a good idea to have a very simple jarvil program that can be tried using one of the cargo commands.

This can be documented in README.rst and then later more examples can be added.

[spino17]

Hey @gabhijit welcome to the repo and thanks for raising this issue. The repo is still under massive changes and documentation is one thing which I accept is falling short. I will surely update the readme.
By the time, you can build the CLI version of the compiler named anyon inside tools dir which then can be set to path. Sequence of the commands to execute hello-world program:

anyon new hello-world
cd hello-world
anyon run

This should execute the main.jv. Let me know if you face in difficulty setting this up.
I would surely updating the docs as well as preparing to host pre-compiled binaries for various os so that even the rust compiler is not required to build it. Thanks again!