readline: add support for ctrl+w and ctrl+u signals

[indexxd]

Add support for regular terminal signals ctrl+w (deletes word back, same as ctrl+backspace behavior) and ctrl+u (deletes entire line) to the readline module.
Currently, these aren't supported but they can be found in other languages (I tried with python and nodejs).

🤖 Generated by Copilot at 24d3718

This pull request enhances the Readline module for Unix systems by adding new actions for deleting the word or the line before the cursor. It modifies the vlib/readline/readline_nix.c.v file to handle the control characters and perform the deletion.

🤖 Generated by Copilot at 24d3718

• Add support for deleting word or line before cursor in readline (link, link, link, link)

• Define new Action enum values for delete_word_left and delete_line (link)
• Handle CTRL + U and CTRL + W key combinations in analyse_control method (link)
• Implement delete_word_left and delete_line methods in Readline struct (link)
• Execute the new actions in read_line method (link)

• Remove unused and incomplete code for handling [ character in readline (link)
  • Delete commented-out block of code in analyse_char method (link)

[spytheman]

Excellent work.