fix(typescript): bundle types at prepublishOnly

[favna]

Please describe the changes this PR makes and why it should be merged:

Note: Also lmk what other repos need these same tooling changes added. I'm not too familiar with the DJS repo stack yet.

This is required to support proper module augmentation with declare module '@discordjs/voice' { } because TypeScript doesn't propegate module augmentations when only targeting the root index.d.ts, even when that file is re-exporting other types.

It's an issue we faced with Sapphire Framework & Pieces and easily fixed by bundling up all the types using Rollup.

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• This PR changes the library's interface (methods or parameters added)
• This PR only includes non-code changes, like changes to documentation, README, etc.

Fixes discordjs/discord.js#6009

[codecov[bot]]

Codecov Report

Merging #149 (3f39ec6) into main (36aad8d) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #149   +/-   ##
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  Coverage   67.74%   67.74%           
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  Files          19       19           
  Lines         896      896           
  Branches      214      220    +6     
=======================================
  Hits          607      607           
  Misses        287      287           
  Partials        2        2           

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[favna]

Converted to draft as I'm making the steps performed here into a CLI lib as you guys recommended me to license it (https://github.com/favware/rollup-type-bundler)

[favna]

Reopened for review as the change to the CLI tool has been made