[Feature] split the size setting of Pen and Eraser

[my-garbage]

Checklist

• I made sure that there are no existing issues - open or closed - to which I could contribute my information.
• I made sure that there are no existing discussions - open or closed - to which I could contribute my information.
• I have read the FAQs inside the app (Menu -> About -> FAQs) and my problem isn't listed.
• I have taken the time to fill in all the required details. I understand that the request will be dismissed otherwise.
• This issue contains only one feature request.
• I have read and understood the contribution guidelines.

Feature description

The pen and the Eraser share the same size setting. Most of the time I need the eraser in a different size.

It could stay same size until the eraser size is changed.

Why do you want this feature?

Because most of the time I need a eraser of a different size as the pen what makes me ruin the pen settings with the eraser and the other way round.

Additional information

No response