QuickLook media. (#447)

* Use QL previews for video and present full screen.
* Use URL(staticString:) in more places.
* Fix DesignKit issues.

DesignKit/Sources/Buttons/ElementCapsuleButtonStyle.swift

@@ -40,6 +40,7 @@ public struct ElementCapsuleButtonStyle: ButtonStyle {
             .multilineTextAlignment(.center)
             .background(background)
             .opacity(configuration.isPressed ? 0.6 : 1)
+            .contentShape(Capsule())
     }
     
     @ViewBuilder

DesignKit/Sources/TextFields/ElementTextFieldStyle.swift

@@ -62,6 +62,7 @@ public struct ElementTextFieldStyle: TextFieldStyle {
             configuration
                 .textFieldStyle(BorderedInputFieldStyle(isEditing: isFocused, isError: isError, returnKey: nil))
                 .focused($isFocused)
+                .onTapGesture { isFocused = true } // Set focus with taps in the space between the border and text field.
             
             if let footerText {
                 Text(footerText)