Compare types of exports

[gabritto]

We should compare the types of what is exported in the declaration file against the inferred types of what is exported in the JS source. This most likely should be used to provide warnings/suggestions, because JS type inference might not be good enough for this to be used as a lint rule. The implementation should also be resilient enough to avoid emitting useless information when inference of JS types doesn't work well.
Example:
js

module.exports.str = "clearly a string"; // Inferred type: "string"

d.ts

export const str: number; // Wrong type

In this case we'd want a warning that the type of str could be wrong.