Write a guide "How to write small and fast Miden contracts in Rust"

@mooori mentioned that this topic came up in discussions.

I'm thinking:

1. Avoid memory allocation.
2. Avoid unaligned memory access (avoid small ints like i8 and i16).
3. Avoid `Vec` and probably other high-level container types. Use arrays.

Felt arithmetic should have near-zero overhead but we want to discourage it (see #999) so I guess we should not promote it here either.

@bitwalker Thoughts?

/cc @bobbinth @Keinberger

查看程式碼庫中現有的 Miden 合約，以了解當前模式和效能考量。查閱 issue #999 以了解 felt 算術的背景。指南應解釋如何為 Miden 編譯器建構 Rust 程式碼，重點關注記憶體分配、資料型別和容器選擇。透過編譯一個小型範例合約並驗證產生的 Miden 組合語言來測試該建議。

由索引模型根據 Issue 內容生成。