add `generate_comments` command

[Dirakon]

trafficstars

eoc generate_comments would look for all comment placeholders in the code (like # <COMMENT-TO-BE-ADDED>) and use LLM to replace them with proper comments.

Proposed cli interface would look like this:

eoc generate_comments\
  --provider=ollama\
  --source=app.eo\
  --comment_placeholder="<COMMENT-TO-BE-ADDED>"\
  --output=out.json\
  --prompt_template=prompt_template.txt

Additionally, some provider-specific command line arguments would also be present.

The output file would contain the corresponding comment for each placeholder.