Fix Javadoc warnings due to Java 21 update (+ some other warnings)

The default implicit constructor must also have a doc comment, so I have to make it explicit and either properly restrict the visibility of the constructor, or actually document it.

pandalib-commands/src/main/java/fr/pandacube/lib/commands/BrigadierCommand.java

@@ -25,6 +25,11 @@ import java.util.function.Predicate;
  */
 public abstract class BrigadierCommand<S> {
 
+    /**
+     * Creates a Brigadier command.
+     */
+    public BrigadierCommand() {}
+
 
     /**
      * Returns a builder for this command.

pandalib-commands/src/main/java/fr/pandacube/lib/commands/BrigadierDispatcher.java

@@ -21,6 +21,11 @@ public abstract class BrigadierDispatcher<S> {
 
     private final CommandDispatcher<S> dispatcher = new CommandDispatcher<>();
 
+    /**
+     * Creates a new Dispatcher instance.
+     */
+    public BrigadierDispatcher() {}
+
 
     /**
      * Registers the provided command node into this dispatcher.

pandalib-commands/src/main/java/fr/pandacube/lib/commands/BrigadierSuggestionsUtil.java

@@ -140,4 +140,8 @@ public class BrigadierSuggestionsUtil {
     }
 
 
+
+    private BrigadierSuggestionsUtil() {}
+
+
 }