Split string into pieces of fixed length and computing q-grams

Is there any existing function that does this?

```R
x <- c("ab", "def", "g")
split_length(x, 1)
#> list(c("a", "b"), c("d", "e", "f"), "g")

split_length(x, 2)
#> list("ab", c("de", "f"), "g")
```

I feel like this has to be a simple application of an existing function, but I can't figure it out.