Add hidpi support

[ArnaudValensi]

Hi,
First I want to say thank you so much for doing this crate ! You make me save a lot of time.

I'm trying to add hidpi support like here: https://github.com/Gekkio/imgui-rs/pull/29/files
But I think I'm missing something.

Here what it looks like without this PR:

And with this PR :/

Do you have an idea about how to solve this?

If you need to use a fake factor, you can set scale_width and scale_height to 2.0.
Also, this PR is based on the commit of the v.2.2

Thank you

[michaelfairley]

Hi!

I recently pushed support for high dpi support onto master in 52ea13c. If it's possible, could you give that commit a try and see if it works for you?

[ArnaudValensi]

It works like a charm, sorry for the disturbance and thank you again.