Initial release of Nightmarish Jitterbug

[Vaans]

• I have followed [proper Hercules code styling][code].
• I have read and understood the [contribution guidelines][cont] before making this PR.
• I am aware that this PR may be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

This pull request introduces the initial release of the Nightmarish's Jitterbug instance, adding new NPCs, quests, instance, and new NPC Skills.

Changes Included

[√] Added NPC_LEX_AETERNA
[√] Added NPC_REVERBERATION
[√] Added NPC_REVERBERATION_ATK
[√] Added new items
[√] Added new monsters
[√] Added new quests
[√] Added Instance

Note: This PR needs to be committed first with #3338 due to the expansion of the skill ID range

This is a conversion of the original files from rA with some modifications to make them work in Hercules.

Issues Addressed
#241

Testing & Validation

Please feel free to report any content missing of failed.