Update JSON.ahk

[robertlzj]

Use Lookup-table is a little more effective.
Test:

t:=["0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F"]
b:=A_TickCount
Loop 1000000{
    y:=""
    Loop 0x10
        ;~ y.= Chr((x:=A_Index-1) + (x<10 ? 48 : 55))   ;23500 ms
        y.=t[A_Index]   ;13063 ms
}
MsgBox % A_TickCount - b
ExitApp

[robertlzj]

Why there is a newline at end of file in my file?
I just eidt the code in brower, and didn't change the end line.