rubico/monad/Stack

## Stack
the stack data structure

## synopsis
```coffeescript
new Stack(values Iterable|any) -> Stack {
map: function,
concat: function,
chain: function,
push: function,
pop: function,
top: function,
}
```

## description
A **Stack** is a data structure that supports `push` and `pop` operations in O(1) time as well as monadic operations that enable iteration, concatenation, and flattening. Items pushed onto a stack are first in last out (FILO).

```javascript [playground]
const myStack = new Stack([1, 2, 3])

console.log(myStack) // Stack [1, 2, 3]

myStack.push(4)
myStack.push(5)
myStack.push(6)

console.log(myStack) // Stack [1, 2, 3, 4, 5, 6]

console.log(myStack.pop()) // 6
```

在原始碼樹中尋找 monad/Stack.js 檔案或類似檔案。此 issue 定義了 API：實作一個包含 push、pop、top、map、concat 和 chain 方法的 Stack 類別。先閱讀專案中現有的 monad 實作，以了解其模式。撰寫測試以驗證 push/pop 的 O(1) 複雜度和單子行為。

由索引模型根據 Issue 內容生成。