Documentation for linking against LAPACK/BLAS

[mattsignorelli]

Since this is probably a common thing, I feel like there should be a section in the documentation for properly linking against LAPACK/BLAS. For example, I developed a binary package and I had to message the Slack to learn which _jll's to use. I saw other people in the Slack had similar issues, and all the answers are slightly different. I also ended up linking against the wrong BLAS (linked LAPACK32_jll to ReferenceBLAS_jll, because I didn't know that ReferenceBLAS32_jll existed).

Just a short section in the documentation that basically says:

For LP64 LAPACK/BLAS, use LAPACK32_jll with either OpenBLAS32_jll or ReferenceBLAS32_jll
for ILP64 LAPACK/BLAS, use LAPACK_jll with either OpenBLAS_jll or ReferenceBLAS_jll

I'd be happy to prepare the wording in a pull request for this