WASD functionality while using elytra

When flying with an elytra, it’s very difficult to look down while retaining your speed. This makes looking for structures from the air difficult, especially in forest biomes. Using direction keys while flying with an elytra should change your direction. Pressing the forward key should make you fly at an increased angle, down should decrease the angle, and strafing should turn. Like with walking, using direction inputs should change the player trajectory a set amount, and not change the way the player is looking. For example, if the player wants to look down while still flying straight, they would press the forward key to tilt their elytra upward, then look downward so that the new flying angle is made parallel to the ground. Additional key inputs could also be useful: Crouching should spread the elytra wings to slow the player’s flight speed, or decrease the speed that’s added by using a firework. This would be useful because, although doing a simple 360 degree turn can also slow flight speed, it doesn't allow for many fine adjustments. Slowing like this could also be useful when a player is in a tight space such as a cave, and a firework would normally send them into the wall or ceiling even if they tried to fly in circles within the space to decelerate.