Add a transform-scale property to all elements and rename scale-x and scale-y

[ogoffart]

• Rename scale-* to transform-scale-* (second commit)
• Add a transform-scale property, make it the default for the -x and -y variant (first commit)
• Also update the examples to use the transform-scale

[ogoffart]

The CI is failing because the home automation demo declares a property scale.
And it is likely that other people have done that so it's a breaking change unfortunately.

[redstrate]

Wouldn't this be a percent property or is it supposed to be float? I see you changed scale-x and scale-y to float, but the default value here is still 100%.

[ogoffart]

percent is not a "normal" type and exist only for the purpose of distinguishing some things that would otherwise have some other units (eg, for width and height or for the value of a color in the rgb function)
But otherwise, this is a float and % values automatically convert to float such that 100% is 1.0

Anyway, this is just a documentation thing in this case. But the true type of these property is float and their default value is 1 which is the same as 100%

[ogoffart]

Updated the PR based on what was discussed at the API review.