Secure PDF Viewer

Notable changes in version 31:

• minor fixes for edge-to-edge support
• fix issue causing the text layer used for text selection to not rotate when the PDF is rotated within the app
• enable hardware memory tagging for use outside of GrapheneOS in the narrow cases where it's available
• update pdf.js to 5.4.149
• update other npm dependencies
• update AndroidX libraries
• update Android SDK and toolchain

See https://github.com/GrapheneOS/PdfViewer/releases/tag/31 for the full release notes.