Make minecraft.mavenizer(repositories) add to top of the list

Traditionally, maven repositories are added like this:
```groovy
repositories {
    maven minecraft.mavenizer
    maven { url = 'https://example.com/repo' }
}
```
In the case of Mavenizer, which we strongly recommend (and require in
most cases) to be at the top of the repositories list, I've updated
`minecraft.mavenizer(repositories)` to do that. You can use it like
this:
```groovy
minecraft.mavenizer repositories
// or
repositories {
    minecraft.mavenizer it
}
```
May be useful for complex setups that add to repositories early.

Author: Jonathing

src/main/java/net/minecraftforge/gradle/MinecraftExtension.java

@@ -51,7 +51,10 @@ public interface MinecraftExtension extends MinecraftMappingsContainer {
      * @see #getMavenizer()
      */
     default MavenArtifactRepository mavenizer(RepositoryHandler repositories) {
-        return repositories.maven(this.getMavenizer());
+        var mavenizer = repositories.maven(this.getMavenizer());
+        repositories.remove(mavenizer);
+        repositories.addFirst(mavenizer);
+        return mavenizer;
     }
 
     /**