[TF2] Feature Request: Killstreak compatibility for Spellbook items

[rabscootle]

Hi!

I was wondering if there was any chance that Spellbook items could increment one's killstreak under one of several (potentially hacky) scenarios:

• Player has any Killstreak item equipped
• Player currently has a Killstreak item drawn out
• Player has a Spellbook item with Killstreaks applied (would require Killstreak Kits for Spellbook items to be added)

[kisak-valve]

Possible duplicate of #2854.