Make boolean flags store_true

[daz]

This enables you to just use the flag --verbose instead of needing to set --verbose=true. Same with the other boolean flags.

[what-the-diff]

PR Summary

• 🔄 Output and SRT Options Update
  Change output_srt and srt_only options to use action="store_true", simplifying their usage.
• 🔊 Verbose Setting Improvement
  Remove the default value for verbose and use action="store_true" for a cleaner implementation.
• 📝 Minor Code Aesthetic
  Add a newline in the get subtitles function for better code readability.

[jytou]

Was going to make the exact same changes. This would be easy to merge and real added value - although we have to be careful that it might break existing automated flows using the non-stored boolean version. Another way to do it is to simply keep the existing ones and add new, stored, ones.