Add possibility to filter messages by reviewer

[JuhanaItkonen]

Descreption
Add possibility to filter based on reviewer. This is because in Muster we would like to use automatic Copilot reviews when PR is opened and send messages to slack on new reviews. We don´t want to have Copilots reviews on slack channel.

[Copilot]

Pull request overview

This PR adds functionality to filter Slack notifications based on reviewer names, specifically to exclude automated Copilot reviews from being sent to Slack channels.

• Adds excludeReviewers configuration option to action definitions
• Implements reviewer filtering in the ReviewStatusAction to skip notifications for excluded reviewers
• Updates the data model to support the new filtering capability

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
README.md	Adds documentation example showing the new excludeReviewers configuration option
Github/SlackJsonFileModel.cs	Extends data models with ExcludeReviewers property to support filtering
Actions/ReviewStatusAction.cs	Implements the filtering logic to skip excluded reviewers

Comments suppressed due to low confidence (1)

README.md:1

• Corrected spelling of 'Descreption' to 'Description'.

[![Docker pulls](https://img.shields.io/docker/pulls/ptcos/slack-json.svg)](https://hub.docker.com/r/ptcos/slack-json/)

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[savpek]

Change is 🍻

However this repo needs some love, dotnet is pretty ancient and ci seems to be bit broken. Any change to fix these issues too since they are required to make new release at this point?

[tarlepp]

at least for me this seems legit, but because this is "old" project, I would ask you first to introduce pr that will remove old (and deprecated Jenkins) Jenkins stuff and replace that with GitHub actions.

ping @savpek , @aeosys