feat(schema): add support for indexes #9
Description
Context
Right now, ormshift doesn't support creating any kind of index as part of migrations, which are essential to build production-ready systems.
Requirements
Start supporting the definition of indexes on the table schema, so they can be added during migrations.
Since there is no exact definition here, proper research has to be done on "what to implement" and "different types of indexes".
Check issue #6, should be similar.