Fix: Selected Item Info for Commodities

[GODrums]

Motivation

By now CSFloat support selling of many different item types. To reflect this in the inventory, we want to display the "List on CSFloat" or "Listed for $..."-buttons for all supported items.
Fixes #271.

Description

This PR reworks the selected_item_info-element according to the current selling capabilities on CSFloat:

• Show "List on CSFloat"-button for Agents, Sticker, Pins, Patches and Cases
• Change the link of the "List on CSFloat"-button to the actual selling page, i.e. https://csfloat.com/sell
• Fixed a bug where the "Charm Detachment Pack" got classified as Charm
• Support stall prices for Agents
  

Implementation notes:

• since we now support items without inspect links (i.e. cases), we now have to re-render the element for every newly selected item. I utilitzed the isLoading-variable for this purpose, but there might be a better approach?
• I decided on using a white-list approach on support item types to stay compatible when new items are added

[Step7750]

Awesome, thanks @GODrums !

A couple small comments, but looks good 👍