REI Search Bar Calculations

Finally got to updating this mod again!

• Updated the calculator functionality to be the same as the one in the most recent version of NEU.
• Fixed a crash when you didn't have REI in your mods folder, now the game tells you you are missing it. (Fix by 0KdGaming)
• Added support for 1.21.6-8 (thanks again KdGaming0)

Please report any issues or suggestions you have in the issues tab or directly in my discord at "bigbou.",

Hope you enjoy using it!