Improve dietline's vi mode ##cons

[xXyepXx]

• Mark this if you consider it ready to merge
• I've added tests (optional)
• I wrote some lines in the book (optional)

Description

• Make the behaviour of some vi commands closer to vim's behaviour.
• Fix some bugs in the word deletion functions.
• Implement c commands (cw, ce, ...).
• Implement vi horizontal motions f/F and t/T and the corresponding delete commands (df<char>, dT<char>, ...).
• Implement dd and cc commands to delete/change the whole line.
• Implement the ~ vi command which swaps the case of the current character.
• Make it possible to submit (by pressing Enter) the line in normal mode (CONTROL_MODE). Currently, we have to go into insert mode and press Enter.

If you're ok with this, I will update the book.

Happy new year!

[trufae]

please rebase instead of using merge commits

[trufae]

there's still 1 warning

dietline.c:215:2: error: ‘i’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
  215 |  memmove (I.buffer.data + start, I.buffer.data + end, I.buffer.length - end);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
dietline.c:233:6: note: ‘i’ was declared here
  233 |  int i;
      |      ^
test -f freebsd-x8

[xXyepXx]

sorry about that, should be fixed now

[trufae]

Amazing pr! I think it all looks good despite few comment style issues but ill be testing it but wanted to congratulate you for your first pr :) thanks!