Add an option to adjust the line width for Bbox edges (#22)

* feat: add bbox thickness option

* feat: add thickness threshold and side option

* fix: clippy

* Minor adjustments

---------

Co-authored-by: jamjamjon <xxyydzml@outlook.com>

examples/yolov8/main.rs

@@ -31,6 +31,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     // build annotate
     let annotator = Annotator::default()
         .with_skeletons(&coco::SKELETONS_16)
+        .with_bboxes_thickness(7)
         .with_saveout("YOLOv8");
 
     // run & annotate