Export public types from Script

[rustaceanrob]

Description

I was developing on the latest commit in master and the script API was missing because it was not annotated with uniffi::export. I did a quick audit of the impl blocks but probably worth another pass by someone else to see if there are impl blocks missing exports

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo fmt and cargo clippy before committing

[thunderbiscuit]

ACK ed7064f.