Deprecate karma-ui5 project

We recommend you to pick a successor from the available UI5 community projects, see https://bestofui5.org/#/packages?search=test-runner.

- Adds a deprecation note to README.md
- Disables dependabot updates, except security updates

JIRA: CPOUI5FOUNDATION-938

.github/dependabot.yml

@@ -4,6 +4,8 @@ updates:
   directory: "/"
   schedule:
     interval: "weekly"
+  # We are only interested in security updates, so we disable all other updates via the following option:
+  open-pull-requests-limit: 0
 - package-ecosystem: npm
   directory: "/"
   schedule:
@@ -18,3 +20,5 @@ updates:
   commit-message:
     prefix: "[DEPENDENCY] "
     prefix-development: "[INTERNAL] "
+  # We are only interested in security updates, so we disable all other updates via the following option:
+  open-pull-requests-limit: 0

README.md

@@ -3,6 +3,9 @@
 [![REUSE status](https://api.reuse.software/badge/github.com/SAP/karma-ui5)](https://api.reuse.software/info/github.com/SAP/karma-ui5)
 [![NPM Version](https://img.shields.io/npm/v/karma-ui5.svg?style=flat)](https://www.npmjs.org/package/karma-ui5)
 
+# DEPRECATED
+**⚠️ This project has been deprecated. We recommend you to pick a successor from the [available UI5 community projects](https://bestofui5.org/#/packages?search=test-runner).**
+
 **Table of Contents**
 - [About](#about)
 - [Quickstart](#quickstart)