Add Hash Plugin for Jarvis

[aandrewchung]

This pull request introduces a new hash plugin to the Jarvis codebase. The plugin enables users to hash strings and files using various hash functions like MD5, SHA1, and SHA256.

Key Changes:

• Added hash.py under jarviscli/plugins, implementing the hashing functionality.
• The plugin supports hashing strings directly from the user input or hashing contents of a specified file.
• Users can select from a range of hash algorithms for their specific needs.

I believe this addition will enhance the functionality of Jarvis by providing a useful utility for security and data verification purposes.

[liu-julia]

Developed in collaboration with Andrew Chung (individual contributions removed in squash). I worked on test_hash.py and Andrew worked on hash.py

[pnhofmann]

Nice work, thanks! Thanks for including tests ;)