Extract example inputs for puzzle markdown

[thesamet]

When solving Advent of Code puzzles, a common repetitive task is manually copying example inputs from the puzzle's markdown file and saving them in the data/examples directory. This process can be tedious and error-prone.

Proposed Solution

Introduce a command that scans the puzzle text for example inputs and writes them to files in data/examples.

Detection Method:

Example inputs are always presented as code blocks (enclosed within triple backticks ```).
In case of multiple code blocks, some may contain outputs, diagrams, or other non-input content. To handle this, the command can prompt the user interactively to confirm which blocks should be saved.

Naming Convention:

If only one input is accepted, it should be saved as ${day}.txt.
If multiple inputs are extracted, they should be named ${day}-{part}.txt.

Expected Workflow

• Run the command (e.g., cargo extract ${day}).
• The tool scans the puzzle markdown file for code blocks.
• If multiple blocks are found, the user is prompted to confirm which ones should be saved.
• Selected example inputs are saved with appropriate filenames.