orm: implement sql_type: 'JSON'

[enghitalo]

Should solve https://discord.com/channels/592103645835821068/592114487759470596/1002632195921432676 and V panic: 'json' is not yet implemented. Please create a new issue at https://github.com/vlang/v/issues/new

module main

[table: 'task']
struct Task {
mut:
	id        string              [primary; serial; sql: serial]
	list_zero []map[string]string [sql_type: 'JSON']
	list_one  string              [sql_type: 'JSON']
}

I pretend implement this soon. Just creating a issue to not forgot.