Add script to create Swift xcframework archive and update Package.swift

Author: tnull

scripts/create_xcframework_archive.sh

@@ -0,0 +1,4 @@
+ditto -c -k --sequesterRsrc --keepParent ./bindings/swift/LDKNodeFFI.xcframework ./bindings/swift/LDKNodeFFI.xcframework.zip || exit 1
+CHECKSUM=`swift package compute-checksum ./bindings/swift/LDKNodeFFI.xcframework.zip` || exit 1
+echo "New checksum: $CHECKSUM" || exit 1
+python3 ./scripts/update_swift_package_checksum.py --checksum "${CHECKSUM}" || exit 1