Suggestion: Plugins, Custom API

Hello team,

Here are few suggestions for new uncovered area of this plugin :
- Dataverse plugin development: pac plugin init, nupkg build, register / pac plugin push, scripts sample for steps / image management
- Dataverse custom api implementation: sample scripts to create custom api with request parameters / response properties

Review the existing Dataverse skills and the PAC CLI coverage before scoping these additions. The requested result is coverage for plugin initialization, package building, registration or push, step and image-management scripts, plus custom API samples with request parameters and response properties.

Written by the indexing model from the issue text.