Weak deps/Extension pkgs on Unitful?

[anandijain]

julia> @time_imports using SBML
      2.5 ms  Zlib_jll
      3.1 ms  Libiconv_jll
      1.8 ms  XML2_jll
     63.9 ms  SBML_jll
      1.9 ms  DocStringExtensions
     10.9 ms  IfElse
      8.6 ms  ConstructionBase
    832.3 ms  Unitful
    160.4 ms  SBML

I usually don't use the Unitful stuff, so maybe it would be a good candidate for https://pkgdocs.julialang.org/dev/creating-packages/#Weak-dependencies

this is off the cuff, no urgency