Fix gutter view positioning and clipping

The gutter view now properly clips its contents and maintains correct positioning
when scrolling. This fixes positioning issues by using the frame's minX instead of
bounds.minX for line number cell placement and adds explicit setting of both x and y
coordinates when positioning the gutter view during layout.

Author: krzyzanowskim

Sources/STTextViewUIKit/Gutter/STGutterView.swift

@@ -92,6 +92,7 @@ open class STGutterView: UIView {
         markerContainerView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
 
         super.init(frame: frame)
+        clipsToBounds = true
         isUserInteractionEnabled = true
         isOpaque = false
 

Sources/STTextViewUIKit/STTextView+Gutter.swift

@@ -35,7 +35,10 @@ extension STTextView {
 
     internal func layoutGutter() {
         if let gutterView {
-            gutterView.frame.origin = contentOffset
+            // gutter view floats on the edge
+            // the contentOffset is the adjustment to make it visible
+            gutterView.frame.origin.x = contentOffset.x
+            gutterView.frame.origin.y = contentOffset.y
             gutterView.frame.size.height = visibleSize.height
             layoutGutterLineNumbers()
         }
@@ -90,7 +93,7 @@ extension STTextView {
 
                 numberCell.frame = CGRect(
                     origin: CGPoint(
-                        x: bounds.minX,
+                        x: frame.minX,
                         y: selectionFrame.origin.y - contentOffset.y
                     ),
                     size: CGSize(
@@ -225,7 +228,7 @@ extension STTextView {
 
                     numberCell.frame = CGRect(
                         origin: CGPoint(
-                            x: bounds.minX,
+                            x: frame.minX,
                             y: lineFragmentFrame.origin.y
                         ),
                         size: CGSize(