fix(typings): import in d.ts files

[smykhailov]

Generated definition files (d.ts) contain an incorrect path to import some of the types if they are used implicitly on static properties. To avoid this, we have to declare types explicitly.
This PR adds the types explicitly.

[codecov]

Codecov Report

Merging #76 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #76   +/-   ##
=======================================
  Coverage   86.29%   86.29%           
=======================================
  Files          39       39           
  Lines         664      664           
  Branches       90       99    +9     
=======================================
  Hits          573      573           
  Misses         88       88           
  Partials        3        3

Impacted Files	Coverage Δ
src/components/Button/Button.tsx	81.08% <ø> (ø)	⬆️
src/components/Accordion/Accordion.tsx	66% <ø> (ø)	⬆️
src/components/Image/Image.tsx	100% <ø> (ø)	⬆️
src/components/Menu/MenuItem.tsx	100% <ø> (ø)	⬆️
src/components/List/List.tsx	100% <ø> (ø)	⬆️
src/components/List/ListItem.tsx	82.35% <ø> (ø)	⬆️
src/components/Menu/Menu.tsx	100% <ø> (ø)	⬆️

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[levithomason]

Heads up, I've merged master and fixed conflicts here for you

[levithomason]

I'm still not sure this is required. This doesn't exist on master yet typings compile, tests pass, and all functionality is working.

Could you recap why we need this again?

[smykhailov]

Whenever you have compiler option "strictNullChecks": true, then it will complain.
This happens only because there is an indexed property defined together with optional. If you use one of them it is fine even with the compiler option enabled

[levithomason]

Approved, merged master, added changelog entry.