docs: Update readme (#1777)

* docs: Update readme

- change to https links
- make links inline
- update md syntax
- add maven central badge
- add event filter (push) to CI badge
- remove release workflow badge
- improve text

* docs: fix maven central badge url

README.md

@@ -1,25 +1,18 @@
-[Grails]: https://grails.org/
-[Groovy]: https://groovy-lang.org/
-[Apache License, Version 2.0]: https://www.apache.org/licenses/LICENSE-2.0.html
+# GORM - Grails Object Relational Mapping
 
-[![Java CI](https://github.com/grails/grails-data-mapping/actions/workflows/gradle.yml/badge.svg)](https://github.com/grails/grails-data-mapping/actions/workflows/gradle.yml)
-[![Release](https://github.com/grails/grails-data-mapping/actions/workflows/release.yml/badge.svg)](https://github.com/grails/grails-data-mapping/actions/workflows/release.yml)
+[![Maven Central](https://img.shields.io/maven-central/v/org.grails/grails-datastore-gorm.svg?label=Maven%20Central)](https://central.sonatype.com/artifact/org.grails/grails-datastore-gorm) [![Java CI](https://github.com/grails/grails-data-mapping/actions/workflows/gradle.yml/badge.svg?event=push)](https://github.com/grails/grails-data-mapping/actions/workflows/gradle.yml)
 
-GORM (Grails Object Mapping)
-===
 
-[Grails][Grails] is a framework used to build web applications with the [Groovy][Groovy] programming language. This project provides the plumbings for the GORM API both for Hibernate and for new implementations of GORM on top of NoSQL datastores.
+[Grails](https://grails.org) is a framework used to build web applications with the [Groovy](https://groovy-lang.org) programming language. This project provides the plumbings for the GORM API both for Hibernate and for new implementations of GORM on top of NoSQL datastores.
 
 
-Getting Started
----
+## Getting Started
 
-For further information see the dedicated websites:
+For further information see the dedicated GORM website:
 
-* [Stable Version](http:https://gorm.grails.org/)
-* [Development Version](http:https://gorm.grails.org/snapshot/)
+* [Latest Release](https:https://gorm.grails.org)
+* [Development Snapshot Version](https:https://gorm.grails.org/snapshot/)
 
-License
----
+## License
 
-Grails and Groovy are licensed under the terms of the [Apache License, Version 2.0][Apache License, Version 2.0].
+Grails and Groovy are licensed under the terms of the [Apache License, Version 2.0](https://www.apache.org/licenses/LICENSE-2.0.html).