Export to Mocha generate unused imports

[senpl]

🚀 Feature Proposal

When import of assert not used do not put it into js file.
Also key and until should not be in exported script, when are not used.

Motivation

Typescript signal it as unused import and potential error. Also export files will be shorter.

Example

IDE Script without assert in generated file will have
const assert = require('assert')//this line is not needed.