feat(ModuleImporter): implement import module compatible with bundlers

[nrauschcom]

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

In this PR, I implemented a ModuleImporter helper class, which currently supports Webpack and File System Imports.

The Util can import all files from a given directory without listing them manually and thus circumvents missed imports.

In an earlier approach [#6102] this issue was solved by doing a file system search, which currently is the only change preventing the use of code bundlers (Webpack, Rollup, etc) in d.js@>13. Read this comment on why bundling is important for some use cases other than Web Development.

My approach will actually just work for File Sytsem import or Webpack, because I'm not very familiar with other bundlers and the implementation seemed not so straightforward. Potentially Rollup works out-of-the-box with rollup-plugin-require-context.

I tested both file system and WebPack in my projects.

I'm open for discussion and feedback.

Close #6681

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating

[nrauschcom]

Sorry, just removed the non-working Rollup implementation that was dangling in my first commit 🙈

[ImRodry]

Can this be done for index.js too? Also doesn't the class need to be declared in the typings?

[nrauschcom]

Can this be done for index.js too? Also doesn't the class need to be declared in the typings?

I think, as long as this util is only used internally (also marked as @private), adding typings serves no use.

For index.js, I think, there is no better way than listing every single export, because the decision which files are in-/excluded is not that trivial and some files only export certain submodules, e.g. Activity: require('./structures/Presence').Activity

[ImRodry]

I think, as long as this util is only used internally (also marked as @private), adding typings serves no use.

Yeah I thought all classes were in the typings but they're not so scrap that

For index.js, I think, there is no better way than listing every single export, because the decision which files are in-/excluded is not that trivial and some files only export certain submodules, e.g. Activity: require('./structures/Presence').Activity

You could probably pass an object with the name of the file as a key and an array (or string?) with the class(es) that should be exported from that file and it would save us a lot of headaches, just gotta see what classes are not exported

[iCrawl]

This needs a rebase.

[vladfrangu]

This needs a rebase

[nrauschcom]

Rebased and adapted imports to node:fs and node:path.

[SpaceEEC]

FS still works fine. Webpack seems sounds, but untested by me.