Check: `is_room_encrypted`

[PenguinBoi12]

Users have to implement manually a check to verify if a user performing a command is in a encrypted room. Since it's a common pattern, we should implement a check for that in checks.py.

Proposed API

def is_room_encrypted() -> Callable:
    async def _is_room_encrypted(ctx: Context) -> bool:
        ...

    def wrapper(cmd: Command) -> Command:
        cmd.check(_is_room_encrypted)

Example

from matrix.checks import is_admin

@_is_room_encrypted()
@bot.command()
async def kick(ctx, user: str) -> None:

Before opening a PR

• Write unit tests
• Run mypy
• Run pytest tests/
• Run black .