As a Watchlist Expiry user, I want the ability to select a custom time period in the dropdown, so I can have a more customized experience.

Acceptance Criteria:

• Add a new field into the dropdown in all relevant places (i..e, watch via star or "watch link, watch via source editor, and watch via action=watch) that is an empty field (_____ days)
• The user should be able to add and save any watch period between 1 day and 181 days