openapi-response-validator: adds response arg to errorTransformer callback (closes #875)

[webketje]

Also added some minor TS typing. Not sure what you mean by "linting" as there are no scripts/ linting configs defined in the repo.

I developed this on Windows and noticed all of the NPM scripts fail with '..' is not recognized as an internal or external command, operable program or batch file. (even with Git Bash). I fixed this locally by running export PATH=$PATH:"../../node_modules/.bin" and replacing the package.json scripts (eg from "test": "../../bin/mocha" to "mocha -r source-map-support/register -r ts-node/register test/**/*.ts").

I also noticed the unit tests use the dist/index.js.. That was kind of unexpected, as the test script loads ts-node anyway and is thus capable of loading index.ts directly (by doing import Sut from '../index' instead of import Sut from '..' in test/data-driven.ts).