feat: executor in rust

[notxorand]

Context

This is a rewrite of the python executor at ./indexify/src/indexify/executor/ in rust. Also includes changes to the .gitignore and README.md files.

What

WIP.

Testing

Contribution Checklist

• [ ] If a Python package was changed, please run make fmt in the package directory.
• [ ] If the server was changed, please run make fmt in server/.
• [ ] Make sure all PR Checks are passing.