Update dependencies

[SimonMarquis]

• Gradle 8.0.2, closes #64
• ktlint-gradle 11.3.1
• AGP 7.4.2
• Jacoco 0.8.8
• Kotlin 1.8.0
• Dokka 1.8.10
• JUnit 4.13.2
• BinaryCompatibilityValidator 0.13.0

This also migrates the 2 remaing Groovy Gradle build files to kts.

[SimonMarquis]

There is one last thing to do, which is to update the "Adding to the Buildscript Classpath".

To me, there is no point of adding the plugin to the classpath this way since we already show how to add it with:

plugins {
  id("com.dropbox.dependency-guard") version "..."
}

Or is it used for something else I did not thought about?

The Legacy Plugin API using the buildscript block feels outdated and is probably no longer used for people wanting to test the snapshot versions.

Could we replace it with something like this?

---

Using SNAPSHOT versions

Snapshot versions are under development and change, but can be used by adding in the snapshot repository

// settings.gradle.kts
pluginManagement {
    repositories {
        maven { url = uri("https://s01.oss.sonatype.org/content/repositories/snapshots") }
    }
}

// build.gradle.kts
plugins {
  id("com.dropbox.dependency-guard") version "x.y.z-SNAPSHOT"
}