One suggestion for improvement: Like so many other web pages for fancy new frameworks and libraries, the github page does not really explain what Flutter is and what problems the Go library can solve.

Can I make a cross-platform GUI with it (a) in the current state, (b) maybe later? If so, what features does it support? How does it compare to Qt, Lazarus, Sciter, Elektron, etc? Does it have internal drag & drop? External drag & drop? Standard file and folder dialogs? Are widgets native or not (I suppose not, but it should be clear from a glance at the page)? Which widgets are supported? Does it have rich text support? Does it have OS-level clipboard support? Does it have transitions or not? Is it themeable? Is it fast? How large are executables built with it? Is it intended for ease of use or somewhat complicated? Do I need to write in other languages (HTML, markup, Javascript) to get things done or can everything be written directly in Go?

All of this is absolutely essential information. Nobody can reasonably decide whether to use this GUI toolkit or not without getting answers to all of the above question. So please, please explain in one sentence what Flutter is and make a section with keyword features.

[Please don't take this wrong, I'm not a naysayer. This is meant as a constructive criticism, not just of this page but of many similar ones. It sure looks like an interesting project.]