feat: add support for nsfw for ThreadChannel

[feelixs]

Pull Request Type

• Feature addition
• Bugfix
• Documentation update
• Code refactor
• Tests improvement
• CI/CD pipeline enhancement
• Other: [Replace with a description]

Description

• added support for accessing the .nsfw property on channels inheriting from ThreadChannel
• Discord doesn't let you change the "age restricted" setting on threads, they always inherit this setting from their parent channel.

Changes

• add .nsfw property to ThreadChannel, inheriting from its parent Text Channel

Related Issues

Test Scenarios

@slash_command(name="show", description="display this channels nsfw setting")
async def show(ctx: SlashContext):
    await ctx.send(str(ctx.channel.nsfw))

• Without this patch, running this command in a thread will raise AttributeError: 'GuildPublicThread' object has no attribute 'nsfw'

Python Compatibility

• I've ensured my code works on Python 3.10.x
• I've ensured my code works on Python 3.11.x

Checklist

• I've run the pre-commit code linter over all edited files
• I've tested my changes on supported Python versions
• I've added tests for my code, if applicable
• I've updated / added documentation, where applicable