Keyboard modifier key icons
**Describe the requested icon**
I'll start with the use case, since it makes it clear _why_ I would like these icons to be added. On macOS (mainly), modifier keys are represented by symbols, when the shortcut is shown, like: ⌘+C, ⌥+⇧+X. `command`, `backspace`, `windows-logo`, `arrow-fat-up`, `arrow-fat-line-up`, `arrow-line-right` and `key-return` are already a part of the collection, and since the unicode characters are inconsistent, I prefer to use the icons when displaying shortcuts.

The missing icons are:
- ^-like for control
- ⌥-like for option
- _something like the backspace icon in reverse_ for delete

**Screenshots**
This is from the shortcuts tab of Google Docs, I find it inconsistent:
![Screenshot from Google Docs](https://user-images.githubusercontent.com/6977583/125605110-d6a8d6ed-50fc-4bdd-9fbc-cbc8876e8e9d.png)

As for the icons to be added, something similar to the character would be the best option in my opinion.

**Additional context**
Add any other context here.
