Investigate conversion of hard-to-replace PNGs to SVG

Almost all graphics in the app are SVG instead of PNG now. There are just a few left that are hard to convert. It may be that some or all of these are impossible to convert, that is unknown and part of the task.

It is certain that this is not a high priority though, as the number of remaining PNGs is so small that any additional compiled app size benefits will be very small.

ankidroid_txt (I have svg format of anki txt if someone wants to try ) drawer_shadow.9 widget_bg_number.9.png widget_bg_small_finish.png widget_bg_small.png widget_bg_time.9.png

Originally posted by @vinishhub in https://github.com/ankidroid/Anki-Android/issues/8707#issuecomment-828659145

@vinishhub - please attach your SVG of ankidroid_txt here if you could? Thank you!