Add repositories standard to Spine SDK by RootPlugin

[alexander-yevsyukov]

This PR teaches the RootPlugin to add the following repositories when it is applied to a project:

repositories {
    mavenLocal()
    mavenCentral()
    maven("https://europe-maven.pkg.dev/spine-event-engine/snapshots")
    maven("https://europe-maven.pkg.dev/spine-event-engine/releases")
}

The repositories are listed in the order they are added.

This is needed to make it easier for new users to apply Spine plugins to a project and get the needed dependencies automatically.

[chatgpt-codex-connector]

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