Import prebid as a module

[Jakeii]

What does this change?

Import the prebid module rather than the built bundle.

Why?

Allows us to use our own bundling tools and browser targets.
Also allows webpack to chunk more effectively (this might not necessarily be good yet! But interesting)

Comparison of bundle analyzer results:
before:

after:

[changeset-bot]

⚠️ No Changeset found

Latest commit: f4f8fc0

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