Updated site-header related components to be more globally usable.

src/components.d.ts

src/components/navigation/menu-item/menu-item.scss

src/components/navigation/menu-item/menu-item.tsx

src/components/navigation/menu-item/readme.md

src/components/navigation/menu-language/menu-language.scss

.../navigation/menu-level-container/menu-level-container.tsx

src/components/navigation/menu/menu.scss

src/components/navigation/menu/menu.tsx

src/components/navigation/menu/readme.md

src/components/site-header/site-header.tsx

src/components/site-header/site-logo/site-logo.tsx

src/components/site-header/site-search/readme.md

src/components/site-header/site-search/site-search.tsx