Allow to keep the original order of the enum values

[bertrandE]

As I understand, the enum values are sorted alphabetically using the "sort" function.

typescript-json-schema/typescript-json-schema.ts

Line 813 in 3d0a280

definition.enum = enumValues.sort();

I am using this library to automatically generate documentation and it would interesting to be able to keep the original order of the enum values (as it might be easier to understand when reading the generated documentation).

It would be nice to have a way of telling TJS to keep the original enum values order defined in the source code.