Ability to Run AdHere on User-Provided URL from Frontend

[KShervington]

Closes #35

Changes

• Changed the first row of the violating sites table to house a text input box
  • Clicking the "Run AdHere" button in this row will run AdHere on the URL the user typed in the input box
  • This replaces one of the sites retrieved from the Ad Experience Report API, so only 9 will be shown now.
• Added constant in ViolatingSitesTable.tsx to control whether or not to filter our nonexistent sites.
• Changed all fetch requests that statically contained backend port number to instead use the port number acquired from the .env file.
• Made several small spacing and style changes to avoid odd visual and usability behaviors.
• Added relevant, supplemental documentation to README files.

Acceptance Criteria

User is able to type a URL into the input text box, in the format shown, run AdHere against that URL, and see fix suggestions.

Example Pictures

Default	Text in Input	Showing Suggestions