Request to support Rolling Thunder rune for Season of Discovery.

Must track Lightning Shield buff, with at least 4 charges, possibly even more. If the threshold is set too low, players might be invited to cast the ability with very little benefit. Effect visuals should be at their peak at 9 charges, inviting the player to cast Earth Shock asap.

Implemented in #196 and improved in #213.

Displays at 7 or more charges of Lightning Shield. More visible with more charges.

A specific handler had to be made, because simply tracking Lightning Shield charges would give false positives if the player did not equip the Rolling Thunder rune.