Formatting error with double-width unicode character

[andrehsu]

For this table, the ⟺ character is double width, but the extension treats it as a single-width character, which results in an unaligned table.

How it looks:

| ¬(A ⟺ B)          | Premise |
| (A ⟹ B) ∧ (B ⟹ A) |         |
|                   |         |

How it should look:

| ¬(A ⟺ B)           | Premise |
| (A ⟹ B) ∧ (B ⟹ A) |         |
|                   |         |