Support the Enhanced Ladders feature of Quark mod.

"Ladders are slightly tweaked to improve your laddering experience:

• Right clicking a ladder with another one will place it, allowing you to drop ladders down without risking falling to your death. ✔
• When on a ladder, looking down will make you slide down the ladder very quickly. ✔

https://github.com/Vazkii/Quark/blob/master/src/main/java/vazkii/quark/tweaks/module/EnhancedLaddersModule.java

worked in 1.16 - backport missing

backport to 1.15 mod version done.
Included in next release