Note editor toolbar new item string as icon

[krmanik]

Pull Request template

Purpose / Description

The Note Editor toolbar add new items as number from 1...N, so I created this PR for adding string / single character as icon for the new items. It helps in recognize the button instead of memorizing button action with the number.

Fixes

Fixes #9077

3. Allow me to change the naming of custom buttons

Approach

1. I have added new variable icon after index.
2. Earlier buttons saved in SharedPrefs as index, prefix and suffix.
   Now when new buttons added it saved to SharedPrefs as index, icon, prefix and suffix

How Has This Been Tested?

Test on Emulator on device

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration (SDK version(s), emulator or physical, etc)

Learning (optional, can help others)

Describe the research stage

Links to blog posts, patterns, libraries or addons used to solve this problem

Checklist

Please, go through these checks before submitting the PR.

• You have not changed whitespace unnecessarily (it makes diffs hard to read)
• You have a descriptive commit message with a short title (first line, max 50 chars).
• Your code follows the style of the project (e.g. never omit braces in if statements)
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• 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

[david-allison]

Looks good! Main question is about the user losing data, which should be handled by

https://github.com/ankidroid/Anki-Android/blob/master/AnkiDroid/src/main/java/com/ichi2/anki/servicelayer/PreferenceUpgradeService.kt

[david-allison]

Looks great!

[mikehardy]

Looks good to me, thank you!