refactor schemas to support sprite2 and sprite3 files, while reusing rules in common with sb2 and
sb3 files
BREAKING CHANGE: Change to main API which now takes an additional boolean argument indicating
whether a sprite or project is being validated
Refactors library to use latest scratch eslint rules. Updates all dependencies to latest versions
which requires minor changes to the JSON schema, tests, and supported engine (8+)
BREAKING CHANGE: Module no longer supports less than Node 8