feat: Implement RepeatNode

[l2hyunwoo]

Issue

close #10

Description

Implement RepeatNode. This node repeats its children N times sequentially.

Additional Context

What if count is zero or below zero?

• count = 0 → Returns empty list (valid: "repeat zero times")
• count < 0 → Throws IllegalArgumentException (fail-fast for logical errors)

This follows Compose's implicit contract where invalid indices cause exceptions (e.g., LazyColumn.items(count)).

inline fun <T> LazyListScope.items(
    items: List<T>,
    noinline key: ((item: T) -> Any)? = null,
    noinline contentType: (item: T) -> Any? = { null },
    crossinline itemContent: @Composable LazyItemScope.(item: T) -> Unit,
) =
    items(
        count = items.size,
        key = if (key != null) { index: Int -> key(items[index]) } else null,
        contentType = { index: Int -> contentType(items[index]) },
    ) {
        itemContent(items[it])
    }

[wisemuji]

I have some suggestions & questions!

[wisemuji]

This logic closely mirrors SequenceNode.collectEvents. If SequenceNode logic is reused or if RepeatNode simply treated its children as an implicit SequenceNode, the code could be DRY-er.
-> This means that test cases will be more concise as well!
-> There's no need to implement this suggestion in the current pull request; it’s just something to keep in mind 🙂

[wisemuji]

LGTM 👏