feat: allow to pass a slice to the preload function

[yansal]

I believe it's more idiomatic for a function to take a slice as a
parameter (vs. a pointer to a slice) to indicate that this function only
mutates the values in the underlying array, and not the length or the
capacity.

For example, that's the case for the sort functions in the standard
library.

[novln]

I'm not sure it will work since you need to mutate the reference of the slice in case you need to resize the capacity of the underlying backing array.
See the bug we have here (#42) when we try with a struct.
Could you add some tests to ensure that this will works as intended ?

[novln]

Perfect 👍