Re-enable the menu buttons

[DikieDick]

Currently the menu buttons are disabled after switching to the new mapping approach.
We want to enable them later, but we still have to investigate whether all the functions work correctly and are properly tested.

The menubar contains buttons for inserting and deleting nodes as well as wrapping and lifting in/from container nodes. With regards to wrapping and lifter #58 exists, but this functionality has largely been implemented already, but not well tested. Testing is also partly tracked in #57.

Concrete list:

1. The line numbers need to be updated on every node change.
2. code entered above in .v files does not appear on its own line.
3. Latex Math mode entered in .v file should appear inside a rocq doc comment.
4. Lifting an input area works but leaves empty lines in place of the input area tags.
5. Select parent does not seem to work correct, having the cursor in a code cell and doing ctrl-. does not allow you to select the code node.

@XyntaxCS could you write a short bit in this description on what still needs to be tested, reviewed, etc. with regards to the insertion and deletion logic?

[XyntaxCS]

So in general there are only two test cases for insertion/deletion which are in nodeupdate.test.ts. This only covers insertion below a node. Hence, the test coverage is very minimal for insertions and deletions. Both @DikieDick and me worked on this and I dont think anyone else reviewed the code yet.

[pimotte]

Item 5 is "just" a visual bug, the code cell is actually selected (delete and wrap nodes become active and function), the border is not highlighted though. Fixed in cb19f82

[pimotte]

Line numbers fixed in e79b512