Update for 1.13-pre7, added api-version: 1.13 in plugin.yml

I haven't properly bumped semantic versioning ever, but going to bump to major version 2 since plugins compiled against 1.13-pre7 API aren't necessarily compatible with 1.12.2 (untested)

Properly added config options for particle effects. Now particles will spawn 1 per tick instead of all in one tick, effectively making the particle effect have a duration. I'd recommend reading the configuration part of the overview for more details, like how specific particles won't work if they require extra data.

Removed outdated intro and added new option descriptions in config.yml