Add Speed Upgrades and Downgrades

[heisluft]

Description

Implemented Speed Upgrades and Speed Downgrades for 1.12 feature parity. Closes #3 .

Discussion

I noticed that due to a bug, when inserting Big filters or upgrades, the Items vanish. Depending on feedback I'll fix the bug for all three items either in this or a separate PR.

Checklist:

• My code follows the style guidelines of this project (.editorconfig, most IDEs will use this for you).
• I have performed a self-review of my own code.
• I have commented my code in areas it may be challenging to understand.
• I have made corresponding changes to the documentation.
• My changes are ready for review from a contributor.

[ThePansmith]

Go ahead and make a separate PR for that

[heisluft]

Will do once this is merged. I'll use #11 to track the issue for upgrades as well.