Migration name allows any character

[jayvdb]

It is possible at the moment to make a migration using a name like add-constraints, which results in a migration directory like .butane/migrations/20240114_013956748_add-constraints/ .

It looks like there is no limitation on characters in the migration name, but I am guessing that quote characters and slashes are going to cause problems, either causing strange errors during migration creation, or later when the embedded migrations are compiled or the migrations are being read back from the file-system.