Refactor unpack and main exported function to return optional zip, if originally provided, in
addition to the validated project.
BREAKING CHANGE: Change to main api to return originally provided zip (or null if string was
provided) along with validated project, in a 2-element array.
Added sb3 schema, renamed sb2 schema, and updated validate to check given input against both sb2 and
sb3 schemas. Validate appends a projectVersion to the given project with 2 or 3 if the given project
is valid against the corresponding schema. Validate now returns an object containing an error
message and both the sb2 and sb3 validation errors upon failure to validate against both schemas.
BREAKING CHANGE: Changes to validate API and what it returns (namely, error returned by validate is
no longer a string, but is now an object which contains an error message string as well as the sb2
errors and the sb3 errors). Users of this library function should expect to parse the given error to
figure out why validation failed.
Resolves issue where sprite counts were inflated due to global variables and lists as well as an
issue where block counts were deflated due to improper handling of nested block structures
GH-10
