Add ProgressIndicator widgets

[FloVanGH]

• Add material ProgressIndicator
• Add fluent ProgressIndicator
• Add native ProgressIndicator
• Add ProgressIndicator documtentation

[tronical]

Looks overall good. I'm unsure about the in-out vs in. What do you think?

Also API wise, I see that minimum, maximum, and value are consistent with other controls, but I wonder if it would be better to have names that make more sense in the context of the progress. But ok, that's not too important.

API wise I'm somehow missing a text. If I were to implement some kind of download dialog, I'd want to also show the progress in percent for example - or display the number of downloaded bytes. But I see that this isn't supported by material design or fluent. So I'd have to build it myself, and then it looks out of place again on the desktop.

Please add a ChangeLog entry.

[FloVanGH]

Looks overall good. I'm unsure about the in-out vs in. What do you think?

Also API wise, I see that minimum, maximum, and value are consistent with other controls, but I wonder if it would be better to have names that make more sense in the context of the progress. But ok, that's not too important.

API wise I'm somehow missing a text. If I were to implement some kind of download dialog, I'd want to also show the progress in percent for example - or display the number of downloaded bytes. But I see that this isn't supported by material design or fluent. So I'd have to build it myself, and then it looks out of place again on the desktop.

Please add a ChangeLog entry.

To rename value to progress makes totally sense.

Yes fluent and material design ProgressBars are without text.

[tronical]

I'd say let's go with this. We can do another round of API review before the next release, but I think this is good to merge - looking forward :)