Update gradle to 8.7 and adjust build.gradle

[bjoernmayer]

This updates Gradle to 8.7.

build.gradle had to be adjusted to the new version:

• maven plugin replaced with maven-publish
• jcenter repository is no more, instead use mavenCentral
• compile was removed, instead implementation has to be used

[bjoernmayer]

@kevinmdavis @molian6 @lindsayismith @yihanzhen

I've read in a different PR, that your notification settings are not set correctly for this repo. Please excuse the direct pings.

As soon as this PR is merged, I'd like to update #92

[yihanzhen]

/gcbrun