Anki add-on: BOUNCER: password protect Anki on startup

This is a security add-on for that acts as a password-protected bouncer for your Anki data. Upon opening the application, Bouncer prompts the user to enter a password to gain access. If the password is inputted incorrectly, the application closes. The default password is "pw" (without quotes, in lowercase), but you can change it to something else in the code if you prefer. I made this because I installed Anki on a shared work computer and don't want other users messing with my decks. If someone tried hard enough, they can find the password in your Anki data files in plain text. This is adequate for my use case. Designed for Anki 2.1.44 on Windows.