fix(types): make transformCommand public

[wutv]

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

Since the method is static, and can be used for more than internal code, it should be classified as public.

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

[monbrey]

In theory, but it's not quite that simple. By making it public, we're no longer able to change or replace it in non-major version since it becomes a public-facing part of the library's interface.

[suneettipirneni]

This was one of the kind of things that I wanted to utilize and expose in the proposed type-utils module, however it's still not confirmed whether this will be a thing or not.

[vladfrangu]

I agree with @monbrey here, might be better as a separate util package instead