Write README

[CRThaze]

Create a basic README describing:

• The purpose of the repository
• Each of the plugins
• Contribution
• Build & Deployment
• Testing

[andreamazza89]

Hi 👋

The company I'm currently working at uses SLOs and is starting to adopt backstage.

I wonder if you could help us understand what this plugin would look like and what features it would offer.

For example, I am guessing that if I select a service and then this plugin, I will see a visual representation of any SLOs that exist for that service. Is that right? Any other features/aspect?

Thank you 😄