Add cut front and back

[etiennecallies]

@olaure01 I saw you had different ideas for Coq and Cut_proof.

Except Coq export, everything should work on preprod: https://linearon.modusponens.dev/

[olaure01]

@etiennecallies I started implementing what is described in the enhancement proposal but I need more time. I will try to push quickly a direct preliminary version (with only the axiomatic approach) for defining and testing the export.

[olaure01]

First test remarks:

• in the pop-up window for cut formula: accept "Enter" to send the formula (currently it is necessary to click on Cut)
• in the pop-up window for cut formula: clear history from one call to the next
• add the cut rule in the list of derivation rules

[etiennecallies]

First test remarks:

• in the pop-up window for cut formula: accept "Enter" to send the formula (currently it is necessary to click on Cut)

Done

• in the pop-up window for cut formula: clear history from one call to the next

I made auto-selection on previously submitted cut formula, so that you can type new one or modify previous one.

• add the cut rule in the list of derivation rules

Yes, done.

[etiennecallies]

@etiennecallies I started implementing what is described in the enhancement proposal but I need more time. I will try to push quickly a direct preliminary version (with only the axiomatic approach) for defining and testing the export.

No problem.

[etiennecallies]

Many thanks @olaure01 ! For me this is ready for merging.

[olaure01]

Fixes #12