fix(deno): Add prepack for deno build

[AbhiPrasad]

fixes https://github.com/getsentry/sentry-javascript/issues/12698

Adds back prepack script just for deno which was removed in https://github.com/getsentry/sentry-javascript/pull/12656 because it's a breaking change for the deno package which relies on the directory structure for their import path.