Asserts the provided buffer has total capacity enough for minimum_len.
Does not advance the buffer end position.
If minimum_len is zero, this is equivalent to unusedCapacitySlice.
pub fn writableSliceGreedy(w: *Writer, minimum_len: usize) Error![]u8
pub fn writableSliceGreedy(w: *Writer, minimum_len: usize) Error![]u8 {
return writableSliceGreedyPreserve(w, 0, minimum_len);
}