Updated code to work with Spicord v5.

You will have to UPDATE Spicord to version 5, this version will not work with Spicord 4

(Requested) Added the %discordrewards_verifycode% placeholder for PlaceholderAPI.

(Requested) Added the {message_count} placeholder to use in the commands of the rewards.yml file.

(Fix) remove member role when unlink

(+) Added /unlink command.
(+) Added "click-to-copy" on code. (1.16+)
(Fix) ConcurrentModificationException when giving reward on join.

IMPORTANT! Update to the latest Spicord version or this plugin wont work.

Various code improvements and compatibiliy for Spicord 4

Added:
- If an user leaves your server and re-joins, it will get back the Verified role and will rename the user to the custom name, this will not re-reward the player.

Bug fixes & improvements

Fully finished the fix of the first issue

Fixed error caused by the previus fix :facepalm:

Fixed non thread-safe method calls.