ERC Extends Bracket Form for Multi-Parameter Keys in Upgrade

ERC-8120 extends ERC-8119 with bracket form for parameterized keys. Bracket syntax [<key-label>][<param-1>][<param-2>]... allows one or more ordered parameters, differing from slash form <key-label>/<key-parameter>. Parameters can be any UTF-8 except ]. Key-labels no longer include the left bracket, making both forms unambiguous. This update aims to provide a clear format for multiple parameter expressions without overloading applications-specific encoding.