feat: implement positional flags

[Vioshim]

Summary

This allows FlagConverters to be used after the first text expression, for example

class HandleText(FlagConverter, prefix="--", delimiter=" "):
    text: str = commands.flag(positional=True)
    flip: bool = False
    
@bot.bridge_command()
async def welcome(ctx: bridge.BridgeContext, *, flags: HandleText):
    text = flags.text[::-1] if flags.flip else flags.text
    await ctx.respond(text)

# ?welcome Hello world
# ?welcome Hello world --flip True
# ?welcome --text Hello world
# ?welcome --text Hello world --flip True

Information

• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed).
• This PR is not a code change (e.g. documentation, README, typehinting,
  examples, ...).

Checklist

• I have searched the open pull requests for duplicates.
• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why.
• I have updated the changelog to include these changes.

[Lulalaby]

@Vioshim please work on dorus comment and resolve conflcts

[Lulalaby]

@Pycord-Development/contributors can we get some testing here :D

[Paillat-dev]

File "C:\Users\Jérémie\Documents\GitHub\pycord\thing.py", line 23, in <module>
    class BasicText(FlagConverter, prefix="--", delimiter=" "):
  File "C:\Users\Jérémie\Documents\GitHub\pycord\thing.py", line 24, in BasicText
    text: str = flag(positional=True)
                ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Jérémie\Documents\GitHub\pycord\discord\ext\commands\flags.py", line 143, in flag
    return Flag(
           ^^^^^
TypeError: Flag.__init__() got an unexpected keyword argument 'name'

The error does not seem to be caused by this PR, but rather by me using python 3.11. The error is not present in my testing when using python 3.10.

fix in #2759

Other than that, this seems to work to me, although I don't think I'm experienced enough with flags - and prefixed commands to assess with good certainty that everything works as expected.

[Lumabots]

does this need testing or is it ready to merge ?

[Paillat-dev]

Needs testing + doesn't work with python 3.11+

[Lulalaby]

Merge conflicts

[Paillat-dev]

@Lulalaby I think that OP is gone but I can fix these in a new pr. Lmk if ok

[Lulalaby]

Sure go for it if you still think it's a good addition

[Vioshim]

My apologies, felt lost on how to be able to contribute in the project once i saw the things about merging conflicts or the documentation changes, so ended up lost on how to correct it alongside irl stuff, so my apologies for the lack of response

[Paillat-dev]

@Vioshim no worries. Do you still want to work on this ? If lmk and I'll handle the merge conflicts and the rest

[Vioshim]

That'd be quite appreciated, thank you!!
@Paillat-dev

[Paillat-dev]

No worries and thank you for your contribution !

[Paillat-dev]

@Lumabots Can I get some testing from you ? Specifically on python 3.11 and higher ?

[Lumabots]

@Lumabots Can I get some testing from you ? Specifically on python 3.11 and higher ?

Yep doing that tomorrow evening

[DA-344]

lgtm code wise, if this is tested and works then should be ready to merge