Add Readme templates.

See spring-projects/spring-data-build#2758

Author: mp911de

.github/README.template.adoc

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+= Spring Data Commons image:https://img.shields.io/badge/Revved%20up%20by-Develocity-06A0CE?logo=Gradle&labelColor=02303A["Revved up by Develocity", link="https://ge.spring.io/scans?search.rootProjectNames=Spring Data Core"]
+
+https://projects.spring.io/spring-data/[Spring Data Commons] is part of the umbrella Spring Data project that provides shared infrastructure across the Spring Data projects. It contains technology neutral repository interfaces as well as a metadata model for persisting Java classes.
+
+Our primary goals are:
+
+* Powerful Repository and custom object-mapping abstractions
+* Support for cross-store persistence
+* Dynamic query generation from query method names
+* Implementation domain base classes providing basic properties
+* Support for transparent auditing (created, last changed)
+* Possibility to integrate custom repository code
+* Easy Spring integration with custom namespace
+
+include::https://raw.githubusercontent.com/spring-projects/spring-data-build/refs/heads/main/etc/readme/code-of-conduct.adoc[]
+
+== Getting Started
+
+include::https://raw.githubusercontent.com/spring-projects/spring-data-build/refs/heads/main/etc/readme/dependencies.adoc[]
+
+include::https://raw.githubusercontent.com/spring-projects/spring-data-build/refs/heads/main/etc/readme/getting-help.adoc[]
+
+include::https://raw.githubusercontent.com/spring-projects/spring-data-build/refs/heads/main/etc/readme/license.adoc[]