[Request] Add dollar sign ($) as a non-standard symbol

The games Sonic Robo Blast 2 and Sonic Robo Blast 2 Kart use the dollar sign symbol for a sort of replacement for assignment operators.

Example 1

local a = 1
a = $ | 2

is equivalent to

local a = 1
a = a | 2

Example 2

local tbl = {
    a = 1
}
tbl.a = $ | 2

is equivalent to

local tbl = {
    a = 1
}
tbl.a = tbl.a | 2

Example 3

playerMo.flags = $ & ~MF_NOGRAVITY

is equivalent to

playerMo.flags = playerMo.flags & ~MF_NOGRAVITY

issue 中沒有指定原始碼檔案或測試。首先定位 Lua 表達式的 parser 或語法分析進入點，並將其與三個範例進行比較；當帶美元符號的形式能夠被接受，並像所示的自我參照表達式一樣處理，同時不破壞標準 Lua 語法時，即表示完成。