Add a basic README file

The project doesn't currently have a README file.

Adding some basic information, example on how to build or what is currently implemented would be a nice start.

Some examples:
https://github.com/apache/arrow-julia/blob/main/README.md
https://github.com/apache/arrow-java/blob/main/README.md
https://github.com/apache/arrow-go/blob/main/README.md