[Feature request] Please add 8 and 16 bit ints for io_variants

[trsh]

8 -> signed char
16 -> signed short

[Danchyg1337]

Instead of creating a new issue, I will add to this one as it's similar.

There are functions to recieve variant from uint16/32/64 but only one function to recieve int32.
It may cause unintentional problems when creating int components with types like io_int16_t*
as then, after accessing the data with [] operator, the data gets read with a wrong stride
const io_int16_t type = comp_type[i];

Two components both with value 1 turn into 1st component being 1 and 2nd being 0.

Just to avoid future problems like this, I propose adding io_variant_from_int* as well.