Freestyle Job Publisher support

### What feature do you want to see added?

This plugin allows for a clean system for interfacing against custom internal applications, without having to deal with the formatting and escaping issues that can come from leveraging the shell block for requests. The existing implementation works well for pipeline jobs, however with Freestyle Jobs the lack of Publisher prevents the ability for a final action based on the results of the build.

Having the publisher added is a minor overall change, but allows the plugin to be fully utilized.

### Upstream changes

_No response_

### Are you interested in contributing this feature?

_No response_

Start by examining how the existing pipeline-job implementation handles HTTP requests and how Freestyle Jobs expose Publisher actions. Define the publisher entry point and verify that a final action can run based on build results without relying on the shell block.

Written by the indexing model from the issue text.