refactor: Add TypeScript support

[fabiovincenzi]

Overview
This PR introduces TypeScript to git-proxy and refactors relevant code to support it.

Changelog

• Added TypeScript configuration (tsconfig.json) with essential settings for strict type checking, ES6 compatibility, and JSX support.
• Added typescript and ts-node to manage TypeScript code compilation and execution.
• Updated the package.json to include TypeScript dependencies.
• Converted the main entry file from JavaScript (index.js) to TypeScript (index.ts).
• Modified the start script to use ts-node for running TypeScript files.

[06kellyjac]

Should be fine to adopt this upstream if you're happy to open a PR.
We might want to double check we build out the right files for publishing but otherwise looks good.
A good pre-req for the db refactor & best to bring this in ahead of that :)

[fabiovincenzi]

Should be fine to adopt this upstream if you're happy to open a PR. We might want to double check we build out the right files for publishing but otherwise looks good. A good pre-req for the db refactor & best to bring this in ahead of that :)

Thanks for the review @06kellyjac !
Yes, I'll open a PR on the upstream then we can go ahead with db refactor.

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