Create stories for Header components

[corwintines]

Create stories for the following header components:

• LanguagePicker
• Nav
• Search

[amit-ksh]

hi @corwintines, I'd like to work on this

[TylerAPfledderer]

Hey @amit-ksh! Making a quick comment here for reference for you and @corwintines.

In review of these components, I believe the only one marked for visual testing would be the Nav, which is fine to start with since it couples the initial rendering of Search and LanguagePicker.

Two thoughts here if we are considering individual stories for this GH issue with Search and LanguagePicker

1. There only needs to be one story for each, but as an interactive test with the play function so that Chromatic can take a snapshot of the open modals.
2. For Search, make sure environment variables used are available in the storybook environment with the testing api keys provided by DocSearch. If not having these keys available in the main .env file, then need to look to the Storybook Config.