Update READMEs

[pbobov]

Change description of the repository

The workflows do not strictly follow all the fundamental GitOps principles. In particular, the workflows automate in-place upgrades of stateful deployments instead of following the "Immutable Infrastructure" principle.

Lets' change the repository's description from "GitOps Templates for ArcGIS Enterprise" to "GitHub Actions for ArcGIS Enterprise" and deemphasize "GitOps" in the root README.

Provide guidance for unclear UX

In particular:

• Though GitHub Actions jobs have outputs, the output values are not shown in the GiHub Actions UI. So far the only way to get the job outputs is to look at the workflows run logs.
• ?

Create diagram for arcgis-enterprise-k8s deployment

Terraform module arcgis-enterprise-k8s/organization should include a system architecture diagram.

[nshampur]

I suggest "ArcGIS Automation using Github Actions"

aligns with other ArcGIS Automation nomenclature.