[doc] core libfuncs : `alloc_local` + array related libfuncs

[TAdev0]

Parent Task: #25

this includes:

    "alloc_local",
    "array_append",
    "array_get",
    "array_len",
    "array_new",
    "array_pop_front",
    "array_pop_front_consume",
    "array_slice",
    "array_snapshot_pop_back",
    "array_snapshot_pop_front",

[TAdev0]

@mazurroman you can assign me to this issue

[TAdev0]

https://docs.google.com/document/d/1Co0Rms68InGbPfp2xWckdrCuom0wIYPmDwWKXimESc0/edit

[TAdev0]

@mazurroman any news about when we can start integrating core libfuncs descriptions?

[mazurroman]

@TAdev0 thanks for staying on top of this. @kwkr is currently looking into adding gas calculation into libfuncs. We should expect at least a couple of weeks before that is ready. After that, I believe we will have everything required to start working on the libfuncs docs.

Will keep you posted!