Support `float: inline-start` and `float: inline-end`

[majdal]

Thanks for the super useful plugin!

I noticed that float: inline-start and float: inline-end are not supported by the package. And of the browsers, they are currently only supported by Firefox:

https://developer.mozilla.org/en-US/docs/Web/CSS/float

I'm guessing that support would look like the following:

.foo {
  float: inline-start;
}

Then translates to:

.foo {
  float: left;
}

html[dir="rtl"] .foo {
  float: right;
}

I haven't written any postcss plugins before, but if the maintainers are ok with it, I can try to create a pull request for the feature. Does that make sense?

[gasolin]

thanks for the suggestion,
welcome to contribute!