feat(checker) : developer can define a function to check license

Could you integrate my changes in your code and publish them (npm publish)?
Thanks
Not wanting to be difficult - but you've added 4 lines here, but changed the spacing of much of the file from tabs to spaces, which impacts more than 50 spaces.  If I merge this I'm going to just set it back to tabs to be consistent.  '

Would you mind fixing this and resubmitting rather than changing and then changing back?