context command to pin messages in respective thread

[ankitsmt211]

Is your feature request related to a problem? Please describe.

A suggestion from community to let OP of thread in questions to be able to pin helpful answers

Describe the solution you'd like

We can build a context menu command something like we already have [Transfer Feature] (application/src/main/java/org/togetherjava/tjbot/features/moderation/TransferQuestionCommand.java) .
It will show up in message context menu, upon clicking that command based on whether user is OP it will either pin the message in thread or reply with an ephermal message that they're not allowed to use that command.

Additional context

• Only OP should be able to use the command
• Put a max limit on number of pins (maybe 10? idk something that's suitable)