Add `NEWS.md` to keep track of/announce changes

[ajinkya-k]

The JuliaLang/julia repo has a NEWS.md which also documented changes in LinearAlgebra. We might need one for this repo

[inkydragon]

Or a CHANGELOG.md, like Pkg.jl: https://github.com/JuliaLang/Pkg.jl/blob/master/CHANGELOG.md

[ajinkya-k]

@inkydragon That makes sense

[ajinkya-k]

This one is kinda important but still not done. Can some of the maintainers take a look?