docs: improve player manager documentation (#1626)

### Motivation
The player manager documentation is outdated and often causes issues in
our support. This should be updated.

### Modification
Updated the documentation of the player manager to provide more
information on how to obtain an instance of it.

### Result
More and better documentation on how to obtain a player manager instance

Author: 0utplay

driver/api/src/main/java/eu/cloudnetservice/driver/registry/Service.java

@@ -32,7 +32,7 @@
  * {@code
  *   @Inject
  *   public TestClass(ServiceRegistry registry) {
- *     var playerManager = registry.firstProvider(PlayerManager.class);
+ *     var playerManager = registry.defaultInstance(PlayerManager.class);
  *     playerManager.onlineCount();
  *   }
  * }

modules/bridge/api/src/main/java/eu/cloudnetservice/modules/bridge/player/PlayerManager.java

@@ -26,10 +26,33 @@
 import org.jetbrains.annotations.Range;
 
 /**
- * The player manager is the main api point to access cloud offline and online players. Accessing the player manager is
- * possible using either {@code ServiceRegistry.first(PlayerManager.class)} or
- * {@code bridgeManagement.playerManager()}.
+ * The player manager provides access to all information cloudnet has about online and offline players. Obtaining an
+ * instance of the player manager is possible through the {@link eu.cloudnetservice.driver.registry.ServiceRegistry}.
+ * <p>
+ * If the player manager needs to be obtained from an injection context, the
+ * {@link eu.cloudnetservice.driver.registry.Service} annotation can be added to the constructor or method.
+ * {@snippet lang = "java":
+ * private final PlayerManager playerManager;
  *
+ * @Inject
+ * public YourClass(@Service PlayerManager playerManager) {
+ *   this.playerManager = playerManager;
+ * }
+ * }
+ * <p>
+ * If the player manager needs to be obtained without an injection context, use
+ * {@link eu.cloudnetservice.driver.registry.ServiceRegistry#defaultInstance(Class)}.
+ * {@snippet lang = "java":
+ * private final PlayerManager playerManager;
+ *
+ * public SomeClass() {
+ *   var serviceRegistry = InjectionLayer.ext().instance(ServiceRegistry.class);
+ *   this.playerManager = serviceRegistry.defaultInstance(PlayerManager.class);
+ * }
+ *}
+ *
+ * @see eu.cloudnetservice.driver.registry.Service
+ * @see eu.cloudnetservice.driver.registry.ServiceRegistry
  * @since 4.0
  */
 public interface PlayerManager {