Bump gdxVersion from 1.13.0 to 1.13.1

Bumps `gdxVersion` from 1.13.0 to 1.13.1.

Updates `com.badlogicgames.gdx:gdx-backend-lwjgl3` from 1.13.0 to 1.13.1
- [Release notes](https://github.com/libgdx/libgdx/releases)
- [Changelog](https://github.com/libgdx/libgdx/blob/master/CHANGES)
- [Commits](libgdx/libgdx@1.13.0...1.13.1)

Updates `com.badlogicgames.gdx:gdx-backend-android` from 1.13.0 to 1.13.1
- [Release notes](https://github.com/libgdx/libgdx/releases)
- [Changelog](https://github.com/libgdx/libgdx/blob/master/CHANGES)
- [Commits](libgdx/libgdx@1.13.0...1.13.1)

Updates `com.badlogicgames.gdx:gdx-backend-gwt` from 1.13.0 to 1.13.1
- [Release notes](https://github.com/libgdx/libgdx/releases)
- [Changelog](https://github.com/libgdx/libgdx/blob/master/CHANGES)
- [Commits](libgdx/libgdx@1.13.0...1.13.1)

Updates `com.badlogicgames.gdx:gdx` from 1.13.0 to 1.13.1
- [Release notes](https://github.com/libgdx/libgdx/releases)
- [Changelog](https://github.com/libgdx/libgdx/blob/master/CHANGES)
- [Commits](libgdx/libgdx@1.13.0...1.13.1)

---
updated-dependencies:
- dependency-name: com.badlogicgames.gdx:gdx-backend-lwjgl3
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: com.badlogicgames.gdx:gdx-backend-android
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: com.badlogicgames.gdx:gdx-backend-gwt
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: com.badlogicgames.gdx:gdx
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

build.gradle

@@ -21,7 +21,7 @@ allprojects {
     version = '1.0'
     ext {
         appName = "Halma"
-        gdxVersion = '1.13.0'
+        gdxVersion = '1.13.1'
 
     }