What kind of change does this PR introduce?
Includes changes requested in #613

Summary

Before committing I had to solve those issues:

• Removed deprecated lang: [0, "always", "eng"] from commitlint configuration. It gave me errors preventing me from committing:

  RangeError: Found invalid rule names: lang. Supported rule names are: body-case, body-empty

• Fixed a tslint error:

 ERROR: packages/migrate/index.ts:20:4 - Type literal has only a call signature — use 
`new(errors: string[]) => {
    message: string;
},` instead.

Those are the actual changes:

1. Adds an interface to transformations in packages/migrate/migrate.ts
2. Refactor every test in migrate/**/__tests__/**.test.ts

//before
defineTest(join(__dirname, ".."), "resolve");

//after
const dirName: string = path.join(__dirname, "..");
defineTest(dirName, "resolve");

3. Adds a type notation in packages/utils/__tests__/ast-utils.test.ts

4. I've also refactored packages/migrate/resolve/__tests__/__testfixtures__/resolve.input.js following this comment.
   There's something I don't understand well, changing const path = require("path") with const {resolve} = require("path") gives me an error:

Why does this happens?

Feedbacks are welcome :)