support global type overrides

[ubogdan]

Is your feature request related to a problem? Please describe.
When using references from generated files (such as from sqlboiler) we encountered a situation where we wanted to override a type (e.g. have null.String, a struct with custom json marshal/unmarshalers, show up in the swagger docs as string instead of as a struct with a string and a bool) but could not use the swaggertype struct tag overrides, as sqlboiler does not allow you to customize those on a per-type basis.

Describe the solution you'd like
It would be nice to have a simple dot file in the same way git has".gitingore". YAML/TOML is too heavy (the libraries are not light at all and it will introduce additional unwanted dependencies) and JSON is not so user-friendly when it comes to editing.

Eventually, we can add the feature to skip packages, without the need to update swag params in the CI pipeline.

Example swag dot file (.swag)

// replace a defintion 
replace database/sql.NullInt64 int64

// skip parsing a package
skip github.com/grpc/grpc-go

Describe alternatives you've considered
NONE

Additional context
#1059

[ubogdan]

the feature will be available since v1.7.7