Support zig errors

[GlowingUmbreon]

Currently zig-webui returns a bool when a error occurs.
It may be worth instead having zig-webui return a error instead of a bool when it sees webui returning a false value to make it easier for users to use zig semantics.

[GlowingUmbreon]

Below is a example of how I am trying to handle errors curently.

var nwin = webui.newWindow();
if (nwin.window_handle == 0) {
    return error.WUI_NEW_WINDOW;
}
defer webui.clean();

if (nwin.setRootFolder("ui") != true) {
    return error.WUI_SET_ROOT_FOLDER;
}
if (nwin.show("index.html") != true) {
    return error.WUI_SHOW;
}

if webui-zig was to support zig errors it could instead look like the following.

var nwin = try webui.newWindow();
defer webui.clean();

try nwin.setRootFolder("ui")
try nwin.show("index.html")

[AlbertShown]

Looks like a good idea to me.

@jinzhongjia What do you think?

[AlbertShown]

@GlowingUmbreon Feel free to suggest a PR if you want.

[jinzhongjia]

I'll achieve this this weekend

[AlbertShown]

Sounds good @jinzhongjia 👍

[GlowingUmbreon]

This would be a breaking change as zig requires any potential errors to be handled by the program. Would this be better to implement on a major release?

[GlowingUmbreon]

Made a quick draft under #92 and added two notes.