This follows the advice given here:
https://latex.org/forum/viewtopic.php?t=32205
The option changes how destination names are defined.

Also fixes two other small typos related to references.

Should address:
#39

- adress normalizing of terms with context push (and other typos)
- Remark on missing Gamma

- replace semantic by semantics
- apply some review suggestions

this looks less ragged

- Define what a valid Alethe proof is formally
- Show that a valid Alethe proof is sound
- TODO: nicer handling of let