Add auto option to body theme

[Kuuuube]

What the auto option does:

• Welcome, settings, permissions, quick start, search, and info pages all use the browser's default theme
• The popup adapts theme based on the theme of the webpage it is being rendered on

I've also set this to be the default. It makes the popups much nicer to read since they don't clash with the page they're being rendered on. This should be a nicer experience for new users.

The reason this pr touches frontend, query-parser, and text-scanner is because information from the parent page is required and due to the popup being a separate webpage this cannot easily be accessed. It is being sent through the same way as other information such as the parent page url and sentence (for later use in anki handlebars).