fix: fileCopyUri should include the URI schema (#527)

BREAKING CHANGE

Make the `fileCopyUri` be an actual URI and include the schema prefix (usually `file:/`)

It already works that way on iOS

android/src/main/java/com/reactnativedocumentpicker/DocumentPickerModule.java

@@ -326,7 +326,7 @@ public static String copyFile(Context context, Uri uri, File destFile) throws IO
           }
           out.close();
           in.close();
-          return destFile.getAbsolutePath();
+          return destFile.toURI().toString();
         } else {
           throw new NullPointerException("Invalid input stream");
         }