[Battle Thread] Notice of icon addition

Added an icon.
Added the icon of the devilish blade that is popular now.
The Devil's Blade icon was borrowed from Mr. Moai.
I haven't implemented the icons for all the characters of Kimetsu no Yaiba yet, but it seems that there is even Purgatory on Moai's site, so I'm thinking of adding it at will.

The Devil's Blade icon can only be used after level 260.

Also, balance the Devil's Forest,
I added the number of stat increases,
The limited-time compensation stage has been updated.
It will be up until tomorrow's manager gets tired.