Update the dependencies and readme file

[sudarshan-koirala]

There isn't mentioned any info about the metaphor api key as well as installation of metaphor_python package in the pyproject.toml file. Hence following changes done.

1. Updated readme with better instructions for creating and activating virtual environment.
2. Updated readme with the metaphor api key and from where to get.
3. Updated the toml file with the metaphor_python package.