Usability suggestions

[Kangaroux]

• Highlight a number within notes when it's selected, e.g. I click on 4 and all of the 4s in my notes become bold
• When adding notes, being able to select a cell with a number to change to that number. This is a minor QoL feature that other apps have, and could be an option for those that find it annoying
• Prevent player from placing an invalid note. There is nothing stopping me from adding a 4 note in a box that already has a 4
• Add more color contrast to notes placed by the player. It's nearly impossible to tell because it's so subtle
• Include a color theme with a lighter background. Even without the black background option checked it's still very dark and a bit harsh on the eyes at night