feat: background color APIs (#11486)

* feat: background color APIs

closes #10519
closes #1564

* clippy

* git branch

* bundle

* fix hex color schema pattern

* add missing `^`

* fix iOS

* revert test

* revert apple-codesign bump

* fmt

* add change files

---------

Co-authored-by: Lucas Nogueira <lucas@tauri.app>

Author: amrbashir

.changes/background-color-apis.md

@@ -0,0 +1,6 @@
+---
+"@tauri-apps/api": minor:feat
+---
+
+Added `Webview::setBackgroundColor`, `WebviewWindow::setBackgroundColor` APIs to set the window background color dynamically
+and a `backgroundColor` window option to set the background color on window creation.

.changes/background-color.md

@@ -0,0 +1,8 @@
+---
+"tauri": minor:feat
+"tauri-utils": minor:feat
+"tauri-runtime": minor:feat
+"tauri-runtime-wry": minor:feat
+---
+
+Added `Window::set_background_color` and `WindowBuilder::background_color`.