Make window both borderless and resizable

[vertexi]

This is a dirty demo. I am sure there is a better way to implement it. Give me some advice please.

[pthom]

Hello,

I appreciate your effort, thanks a lot!

However, there is probably a simpler, without hacking ShowMenuBar.

Since it seems like a potentially interesting feature, I worked on a draft: you can find it here in the branch borderless_resizable

https://github.com/pthom/hello_imgui/tree/borderless_resizable

See commit 9976758afc8ae30af97364c22b562ccc4767f7c8

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If you wish, you could continue based on this draft.