Filter quests containing a specific item about priconne-quest-helper

[Expugn]

I've added this feature in commit 08cf0bd.

To "focus" on an item, go to the Items tab and click on any item in any category. Any quest containing that item will then be displayed.

Focus can be switched by selecting on another item or removed if you click on the focused item.

Also, thanks for taking the time to write that pull request (#13)! However, the implementation seemed too complicated so I ended up writing my own. Even though I ended up not using your code in the end it was still a great visualization on what you wanted!

[alexanderabramov]

For example, filter for "Emerald Earrings Fragment":

Whereas normally, these quests would be very far down the list