Bump version number to 1.3.1-SNAPSHOT

CHANGELOG.md

 # Changelog
 
+## [(next version)](https://gitlab.cs.uni-duesseldorf.de/api/v4/projects/848/jobs/artifacts/master/raw/build/libs/prob2-jupyter-kernel-1.3.1-SNAPSHOT-all.jar?job=test)
+
 ## [1.3.0](https://www3.hhu.de/stups/downloads/prob2-jupyter/prob2-jupyter-kernel-1.3.0-all.jar)
 
 * Added support for Java 17.

README.md

@@ -10,7 +10,7 @@ This is a [Jupyter](https://jupyter.org/) kernel for the [ProB animator and mode
 
 * **[Download the latest version of the ProB2 Jupyter kernel here](https://www3.hhu.de/stups/downloads/prob2-jupyter/prob2-jupyter-kernel-1.3.0-all.jar).**
 * Download links for previous versions can be found in the [changelog].
-* A [snapshot build](https://gitlab.cs.uni-duesseldorf.de/api/v4/projects/848/jobs/artifacts/master/raw/build/libs/prob2-jupyter-kernel-1.2.1-SNAPSHOT-all.jar?job=test) of the latest development version is also available. **Warning:** this is an unstable version that can contain bugs or breaking changes.
+* A [snapshot build](https://gitlab.cs.uni-duesseldorf.de/api/v4/projects/848/jobs/artifacts/master/raw/build/libs/prob2-jupyter-kernel-1.3.1-SNAPSHOT-all.jar?job=test) of the latest development version is also available. **Warning:** this is an unstable version that can contain bugs or breaking changes.
 
 See the [requirements](#requirements) and [installation instructions](#installation) for information on how to install and use the downloaded jar file.
 

build.gradle

@@ -9,7 +9,7 @@ plugins {
 	id("com.github.johnrengelman.shadow").version("7.1.2")
 }
 
-version = "1.3.0"
+version = "1.3.1-SNAPSHOT"
 
 final isSnapshot = project.version.endsWith("-SNAPSHOT")