Clarify difference between piping text to mods with -p, -P or no flags

[gy-mate]

Describe the bug
The difference between using mods...

• with the -P flag
• with the -p flag
• without any flags

...when piping a text to the command isn't clear to me. I think that this should be clarified in README.md and features.md.

Setup

• OS: macOS 15.2
• Shell: zsh
• Terminal Emulator: Warp
• Terminal Multiplexer: N/A

To Reproduce
All the following commands result in basically the same answer:

echo "class Subway:" | mods "Please write me an __init__() for this class."

echo "class Subway:" | mods -p "Please write me an __init__() for this class."

echo "class Subway:" | mods -P "Please write me an __init__() for this class."

Additional context
As asked here: https://discord.com/channels/1032368467246075914/1032368467988451425/1314985081030578247

[caarlos0]

what do you feel is insufficient about mods --help in that regard?