Add degreeFahrenheit and temperatures aliases/shortcuts

[hellmrf]

This PR:

• Adds the unit degreeFahrenheit, similar to the existing degreeCelsius;
• Adds the unit fahrenheit as an alias to degreeFahrenheit;
• Adds the unit celsius as an alias to degreeCelsius;

Example

Working example:

#import "/src/lib.typ": qty

$ qty(10, "degreeCelsius") = qty(10, "celsius") $
$ qty(10, "degreeFahrenheit") = qty(10, "fahrenheit") $

Output: