Include common names for Magisk app in list of flashable zip files.

We introduce a new XML element prfxfilter for file name prefix
filtering, e.g. Magisk- .

The file is first matched against the list of extensions and, if there's
no match, then matched against the list of prefixes. An extension or
prefix may be equal to the whole filename.

Change-Id: I46a985c7298799793911948bc74296bebb306d9e
diff --git a/gui/theme/common/watch.xml b/gui/theme/common/watch.xml
index 05438a6..50f3c2b 100755
--- a/gui/theme/common/watch.xml
+++ b/gui/theme/common/watch.xml
@@ -399,6 +399,7 @@
 				<placement x="%indent%" y="%row2_header_y%" w="%content_width%" h="%fileselector_install_height%"/>
 				<text>%tw_zip_location%</text>
 				<filter extn=".zip;.ozip;.ZIP;.OZIP" folders="1" files="1"/>
+				<prfxfilter prfx="Magisk-;Magisk.apk;app-release.apk;app-debug.apk" folders="1" files="1"/>
 				<path name="tw_zip_location" default="/sdcard"/>
 				<data name="tw_filename"/>
 				<selection name="tw_file"/>