Added new lead_friend and lead_enemy particles and sounds, to make it clear when a "lead" behavior begins

New animated lead particle (arrows pointing where they are going). New animated attack particles with random # of particles.

New follow, flee, attack, and protect particles & sound effects. Protect now auto sets friendship to 1 (if <= 0), to prevent entity from attacking and protecting at the same time. Passive entities no longer emit damage particles when attacking, they emit custom attack particles

Initial custom particles, and a custom particle type and factor for friendship particles (heart and fire)

Updated README.md with new video thumbnail, and simplified text, added spoiler to install instructions

Updating README.md, renaming COPYING to LICENSE.md (replacing with markdown version of GPLv3), updating screenshots to owlmaddie versions.

- Removing example mixins (from Fabric starter project)
- Replacing old screenshots
- Added Discord invite link to README