convert typing-dependencies as dev-dependencies

[jkowalleck]

some runtime-dependencies are actually dev-dependencies:

• typed-ast
• types-setuptools
• types-tom

acc / cit

• the deps are not installed per default, if this package is installed.

as they might be needed by others in upstream, we still might add them es an extra called "typing"

[jkowalleck]

@madpah this feature has the lowest prio of them all.
it did not work at the first try, and it might have impact on other downstream projects.
so i hereby close this PR and reject my feature request.