Make three-stdlib be an external dependency

[minisheeep]

Description

My Rollup plugin performs some work based on whether certain exports from three-stdlib are used, such as DRACOLoader. I would like it to be handled when using cientos as well.

Suggested solution

Release a version without builtin three-stdlib

Alternative

No response

Additional context

No response

Validations

• I agree to follow this project's Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.