Add `matfrostfunction` macro

[jorisbelierasml]

i.e. a @matfrostfunction macro that will do:

1. Check validity of function to be exposed.
2. Add precompilation statements
3. Create cfunction to be used in MEX.

For:

@matfrostfunction function broadcast_multiply(c::Float64, v::Vector{Float64})...

1. Check validity.
   a. Are types concrete entirely
   b. Does function have only a single method implementation.

2. Create the

function _matfrostfunction_broadcast_multiply(mfa::MATFrostArray)...

3. Create a function to pull c function pointers

_matfrostfunction_c_broadcast_multiply() = @cfunction(matfrostfunction_broadcast_multiply, MATFrostArray, (MATFrostArray,))

4. Add precompilation statements. (If necessary.)