More Projectile API

Co-authored-by: Nassim Jahnke <nassim@njahnke.dev>
Co-authored-by: SoSeDiK <mrsosedik@gmail.com>
Co-authored-by: MelnCat <melncatuwu@gmail.com>

paper-api/src/main/java/org/bukkit/projectiles/ProjectileSource.java

@@ -39,4 +39,26 @@ public interface ProjectileSource {
      */
     @NotNull
     public <T extends Projectile> T launchProjectile(@NotNull Class<? extends T> projectile, @Nullable Vector velocity);
+    
+    // Paper start - add consumer to launchProjectile
+    /**
+     * Launches a {@link Projectile} from the ProjectileSource with an
+     * initial velocity, with the supplied function run before the
+     * entity is added to the world.
+     * <br>
+     * Note that when the function is run, the entity will not be actually in
+     * the world. Any operation involving such as teleporting the entity is undefined
+     * until after this function returns.
+     * <p>
+     * The family of launchProjectile methods only promise the ability to launch projectile types
+     * that the {@link ProjectileSource} is capable of firing in vanilla.
+     * Any other types of projectiles *may* be implemented but are not part of the method contract.
+     * @param <T> a projectile subclass
+     * @param projectile class of the projectile to launch
+     * @param velocity the velocity with which to launch
+     * @param function the function to be run before the entity is spawned
+     * @return the launched projectile
+     */
+    <T extends Projectile> @NotNull T launchProjectile(@NotNull Class<? extends T> projectile, @Nullable Vector velocity, java.util.function.@Nullable Consumer<? super T> function);
+    // Paper end - add consumer to launchProjectile
 }