Add superscripts for Greek letters

Please read the formatting guidelines explained in #5 to contribute!

When submitting, you may choose to leave some symbols for others to contribute.

Before submitting a PR check:

* There are no active pull requests for the symbol you are submitting
* You have proper tabs between characters as explained in #5 (you can copy paste tab symbol from other lines)

### Symbols to add

These are the only remaining Greek letters supporting superscript as far as I know:

```
^Phi ᶲ
```

----

### Added already (#56, #59, #60):

```
^alpha ᵅ
^beta ᵝ
^chi ᵡ
^delta ᵟ
^gamma ᵞ
^iota ᶥ
^phi ᵠ
^theta ᶿ
^epsilon ᵋ
```

Read the formatting guidelines in issue #5 and inspect the existing dictionary entries for tab spacing and symbol format. Confirm that no active pull request covers Phi, then add the remaining ^Phi entry with the specified superscript character and verify its formatting against nearby lines.

Written by the indexing model from the issue text.