JSON <-> Constant conversion for EIP-24, EIP-34 #194
Description
Analogous to ergoplatform/sigma-rust#611, we need appkit to support conversion between json to ErgoValue and vice versa. Or at the very least, support types introduced in EIP-24 and 34.
The motivation behind this is explained here by @aslesarenko: ergoplatform/eips#69 (comment)