Refence: Demo Defence

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* Reduce the max wave by 20 and add a very cheap max wave research node for a better early game experience
* Add hero Jax to the demo and raise the max difficulty to 3
* Add a research node for choosing between XP and Lv wave rewards
* Add a research node to spawn a wave of goblins
* Remove the shield from Loot Goblin
* Fix the bug where Aella's skill is not working properly at low FPS
* Boost Critical related traits and researches
More can be found in the in-game changelog.