Adding ability to add custom sort params to @OrderBy params

[felipesabino]

orderBy sort column auto-generated array now can be extended to have custom fields as pleased instead of just having the fields from returned object provided on Field decorator.

This is passed as an array to the OrderBy decorator, and all strings passed will be added as possible sort columns to the schema.

Example:

@OrderBy(['extraField']) orderBy?: OrderByItem[] // 'extraField' is added as a possible value to the sort enum

Also fixed some typos on error messages