More mathematical symbol icons
**Describe the requested icon**
Explain the icon you'd like to see, and potential use-cases.

It would be nice to have symbols for some more of the common mathematical symbols. 

Some examples are <, ≤, >, ≥, ≠, ≈, ∈, and ∉.

**Screenshots**

I think the characters are enough!

**Additional context**
N/A
