* chore: update type testing setup * stricter TSConfig * deduplicate type checking
- some indirect dependencies install @types packages which are not compatible with the older typescript. - adjusted test's tsconfig to not pick these up automatically, as the actual .d.ts does not depend on these external types.
- Move typings from lib/ to types/. - Add dtslint for validating types. - Use grunt-bg-shell to call out to dtslint during build step.