[Feature Request] Backpack sellall stopgaps

[aikaterna]

Feature request

Complete these first

• I confirm that I have checked the issue tracker and a this feature request doesn't already exist.

Select the type of feature you are requesting:

• Command
• Functionality

Describe your requested feature

If someone types a rarity wrong it shouldn't default to a sellall.

If someone types something like [p]backpack sellall nermal the bot will respond with "Are you sure you want to sell all items in your inventory?" - Ideally it would be nice if the bot could say something like the rarity "error" of "I've never heard of nermal rarity items before."

The rarity or sell all definition should be bolded as well:
Are you sure you want to sell all normal items in your inventory?
Are you sure you want to sell all items in your inventory?

[aikaterna]

Yes, this is directly related to #325 but I've got ideas in this one on how I want it implemented since people can't read and just blindly hit the yes button.