Undo stroke in drawing editor

[leobugeja]

Description

The drawing editor did not have any way of undoing a stroke so it was proposed to add an undo button.

Even before this change, when the whiteboard is enabled during a card review, there is an eraser menu icon which undos strokes:

Therefore the same implementation was used for the drawing editor and the same eraser icon was used for consistency. However, its possible the icon could be mistaken for an eraser drawing tool, therefore the undo icon could be a good alternative.

With eraser icon (as implemented in this PR):

Undo icon as alterntive option:

Lastly when there are no strokes to erase, the icon is disabled but remains visible.

Fixes

• Fixes #16241

Video Demo

undo_tool_demo.webm

Checklist

• [x] You have a descriptive commit message with a short title (first line, max 50 chars).
• [x] You have commented your code, particularly in hard-to-understand areas
• [x] You have performed a self-review of your own code
• [x] UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• [ ] UI Changes: You have tested your change using the Google Accessibility Scanner

[welcome[bot]]

First PR! 🚀 We sincerely appreciate that you have taken the time to propose a change to AnkiDroid! Please have patience with us as we are all volunteers - we will get to this as soon as possible.