Added "corners" argument to ImageDraw rounded_rectangle()

[radarhere]

Resolves #6953, by adding a corners argument to ImageDraw.rounded_rectangle - a tuple of booleans for whether or not to round each corner, going clockwise, starting with top left and ending with bottom left.

[hugovk]

Re: https://understandlegacycode.com/blog/what-is-wrong-with-boolean-parameters/

Rather than something like:

rounded_rectangle((10, 20, 190, 180), 30, (True, False, True, True))

Would it be better if we made corners a required keyword argument?

rounded_rectangle((10, 20, 190, 180), 30, rounded=(True, False, True, True))

[radarhere]

Ok, I've pushed a commit to only allow corners to be used as a keyword argument.

>>> draw.rounded_rectangle((10, 20, 190, 180), 30, "red", "green", 5, (True, True, True, True))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: rounded_rectangle() takes from 2 to 6 positional arguments but 7 were given
>>> draw.rounded_rectangle((10, 20, 190, 180), 30, "red", "green", 5, corners=(True, True, True, True))
>>> 

[hugovk]

Or something like this for more transparency? Better for help(rounded_rectangle) and so on.

Suggested change

	self, xy, radius=0, fill=None, outline=None, width=1, **kwargs
	self, xy, radius=0, fill=None, outline=None, width=1, *, corners=None

Or even this?

Suggested change

	self, xy, radius=0, fill=None, outline=None, width=1, **kwargs
	self, xy, radius=0, fill=None, outline=None, width=1, *, corners=(True, True, True, True)

(And update/delete the below to match.)

[ChrisMGeo]

I think corners=(True, True, True, True) is best. But what would the ordering be? Top left, top right, bottom right, bottom left (clock wise)?

[radarhere]

I've updated the commit to use the first suggestion.

As for the ordering, yes, that is the ordering I've used. It mirrors the ordering in CSS for border-radius.