File based nushell kv-module

• Why does this module exist, as we already have the fine std-rfc/kv module?
• I started developing and using this module a long time ago, and my scripts already use it. Additionally, this module relies on version-control friendly local files, rather than on an SQLite database, which also provides some advantages for me. So I continue its development.

Features

• Autocompletion for key names
• Ability to set folders to save objects (via $env.kv.path or by using the kv set --cwd flag)
• Ability to alter variable names using $env.kv.keys-suffix (useful for debugging modules inside bulk tests)
• Timestamped history of all versions of objects

Acknowledgment

The initial version of this module was created by @clipplerblood and shared on the discord.