Applies the theme to all board pages and catalog. Fixes #39.

This PR fixes #39.

I've added the `styles` variable in the `catalog.html` template.

I have also edited the `matchers` regex in `templates/main.js` to include the following cases:
- `https://8chan.co/<board>/<digit>.html`
- `https://8chan.co/<board>/catalog.html`

@ctrlcctrlv, this change makes it so that `$config['catalog_link']` needs to be defined (it comes commented-out by default in `inc/config.php`), because it calls config.catalog_link to create the `matches` regex.
Do you think I should uncomment it so that new installations don't break?

Additionally, I have added the `config.root` option to the stylesheet `href`, so that those of us developing locally can host Tinyboard in a subdirectory without breaking the stylesheets' urls.

@ctrlcctrlv, I'm kind of insecure if the `config.root` thing will break when put into production, so it would be nice if you double checked that. Thanks!