Generate .d.ts (declaration files) instead of using regular .ts files

[tahminator]

Hello!

This PR updates the SDK to output .d.ts files in place of .ts as is usually the norm for TypeScript library files.

I made this PR because in my current project, I'm working on migrating our Bash scripts to Bun shell (& TS SDKs) and part of that includes moving our DigitalOcean infrastructure definitions to dots

However, I'm currently running into an issue where the .ts files are explicitly being checked by tsc even when being included in the exclude array. From my research online, it seems like the fix is to use skipLibCheck but that only works if your libraries are using declaration files instead of traditional TS source files.

I manually ran a test where I generated .d.ts files from dots instead (and trash'd all the .ts files) and it did seem to work:

Before:

After:

I excluded .ts source files from ending up in the final package by adding a .npmignore file into the root dir, which should be enough