Add duration and a condition to the Shield Mechanic

Summary

I believe the Shield mechanic is lacking currently and could be improved hugely with these steps!

1. Add a duration how long the shield can last.

2. Add a condition check if a mob has a shield active so you can use particle effects to display a shield on them.

Condition example: https://pastebin.com/NVtUEcsc

Duration example: https://pastebin.com/nZzMGx00

Usage

It would people use this mechanic more often as its not very good at the moment.

Value

This would add more functionality to the shield mechanic and more interesting bosses you could make overall.

Priority

Medium, i think it would benefit the plugin greatly but bugs come first!

Implementation

Already stated up above on the summary section.