Documentation: add description of parameters and functionality

[GenevieveBuckley]

Constantin gave a good user tip in this comment. I think it's a good tip, and it would be nice to include/highlight this in the micro-sam documentation.

#196 (comment)

I've found it helps to get your line close to the edge of the object you want to segment. Too far inside or outside give you poorer results (understandable, and I didn't find it too annoying - there is a little bit of flexibility & you don't have to be too precise)

In these cases it might help to increase the box_extension parameter.

[constantinpape]

In general: parameters and functionality need to be documented better.
This is def. on my agenda, but I am a bit hesitant to invest much time now, since the user interface will change a bit with all the changes for the plugin. I have renamed the issue to broaden the scope a bit.
For now, let's collect relevant links here. I will start with two forum threads with user questions about parameters and finetuning:

• https://forum.image.sc/t/tracking-fast-moving-cells/86389
• https://forum.image.sc/t/finetune-micro-sam-on-your-own-data/86544

[constantinpape]

I am closing this in favor of #501. Note that we also have tooltips for the UI now which we can use for documenting the parameters.