feat: update capabilities and add clipboard image reading functionality for Linux

- Updated capabilities.json to allow opening shell commands.
- Implemented read_clipboard_image function for Linux using arboard to read images from the clipboard and encode them as base64 PNG.
- Added a stub for read_clipboard_image on non-Linux platforms.
- Registered the new command in the Tauri application.

src-tauri/Cargo.toml

@@ -25,6 +25,11 @@ tauri = { version = "2", features = ["devtools"] }
 tauri-plugin-shell = "2"
 tauri-plugin-notification = "2"
 
+[target."cfg(target_os = \"linux\")".dependencies]
+arboard = { version = "3", features = ["wayland-data-control"] }
+png = "0.17"
+base64 = "0.22"
+
 [target."cfg(any(target_os = \"android\", target_os = \"ios\"))".dependencies]
 tauri-plugin-deep-link = "2"