Slice method 🔪❗ for the List 🍨 class

[Joe Skeen]

⭐️ Proposed change

Emojicode already has a way to "slice" (substring) a string (🔪❗), but the List class 🍨 does not have a similar feature.

🤔 Rationale

When writing the regular expression engine, I found it easier to work with lists of graphemes than strings, but I also need to be able to create "substrings" from the array, and didn't want to constantly have to convert it back into a string to do so.

🕺 Example

🔪🍿0 1 2 3 4 5 6 7 8 9🍆 2 4❗ 💭 returns 🍿2 3 4 5🍆
🔪🍿0 1 2 3 4 5 6 7 8 9🍆 10 6❗ 💭 returns 🆕🍨🐚🔢🍆❗
🔪🍿0 1 2 3 4 5 6 7 8 9🍆 7 6❗ 💭 returns 🍿7 8 9🍆