Bring back the GOALS file.
I still find it useful to track the end goals and inform readers
and interested contributors.
I think copyleft-next won't have a preamble yet, and the GOALS file
serves to work on them in a separate file, avoiding changes to the
license file during its drafting.

Signed-off-by: enyst <engel.nyst@gmail.com>
Document how goals have been achieved. Add license compatibility goal.

Signed-off-by: enyst <engel.nyst@gmail.com>
Add rationale.
Clarifies that while all goals are important, the reason for
copyleft-next to exist is to offer an improved instrument
against copyright privilege.

Signed-off-by: enyst <engel.nyst@gmail.com>