feat: background color APIs

[amrbashir]

closes #10519
closes #1564

needs: tauri-apps/tao#995

[github-actions]

Package Changes Through bf3c384

There are 9 changes which include tauri-utils with minor, tauri with minor, @tauri-apps/api with minor, tauri-bundler with minor, tauri-cli with minor, @tauri-apps/cli with minor, tauri-runtime-wry with minor, tauri-macros with patch, tauri-runtime with minor

Planned Package Versions

The following package releases are the planned based on the context of changes in this pull request.

package	current	next
@tauri-apps/api	2.0.3	2.1.0
tauri-utils	2.0.2	2.1.0
tauri-bundler	2.0.4	2.1.0
tauri-runtime	2.1.1	2.2.0
tauri-runtime-wry	2.1.2	2.2.0
tauri-codegen	2.0.2	2.0.3
tauri-macros	2.0.2	2.0.3
tauri-plugin	2.0.2	2.0.3
tauri-build	2.0.2	2.0.3
tauri	2.0.6	2.1.0
@tauri-apps/cli	2.0.4	2.1.0
tauri-cli	2.0.4	2.1.0

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[dionysuzx]

is it possible to set it different on dark vs light mode? @amrbashir (on backend, so like when it starts up, fetching first from system)

[amrbashir]

you'd have to get the theme first before creating the window and then create the window with the color you want through Rust not in the config.