Allow capturing dialog window content instead of Activities window

[AlanCornthwaiteKatalyst]

The Issue #150

The HotwireViewScreenshotHolder was using the Activity window to capture snapshots via PixelCopy. When a web view was inside a BottomSheetDialogFragment (which has its own Dialog and Window), the snapshotting process would accidentally capture the content of the Activity window sitting behind the bottom sheet at that same screen position. This resulted in the background content appearing in the foreground modal as it was dismissed.

The Fix

• Updated HotwireViewScreenshotHolder: Modified the captureScreenshot method to accept an optional Window parameter. If provided, it uses this specific window for PixelCopy; otherwise, it falls back to the activity window as before.
• Updated HotwireWebFragmentDelegate: Enhanced the screenshotView() method to check if the current destination fragment is a DialogFragment. If it is, it now retrieves the dialog.window and passes it to the screenshot holder.

[mbarta]

Thank you for your contribution! I've included the changes in #217 which will be part of the next library release.