scale markers as well (#1839)

lib/extensions/commands_scale_symbols.py

@@ -21,3 +21,8 @@ class CommandsScaleSymbols(InkstitchExtension):
         for symbol in command_symbols:
             transform = Transform(symbol.get('transform')).add_scale(size)
             symbol.set('transform', str(transform))
+
+        markers = svg.xpath(".//svg:marker[starts-with(@id, 'inkstitch')]", namespaces=NSS)
+        for marker in markers:
+            marker_size = float(marker.get('markerWidth', 0.5)) * size
+            marker.set('markerWidth', marker_size)

symbols/marker.svg

@@ -20,7 +20,10 @@
        refX="10"
        refY="5"
        orient="auto"
-       id="inkstitch-pattern-marker">
+       id="inkstitch-pattern-marker"
+       markerUnits="userSpaceOnUse"
+       markerWidth="0.5"
+       viewBox="0 0 1 1">
       <g
          id="inkstitch-pattern-group">
         <path
@@ -37,7 +40,10 @@
       refX="10"
       refY="5"
       orient="auto"
-      id="inkstitch-guide-line-marker">
+      id="inkstitch-guide-line-marker"
+      markerUnits="userSpaceOnUse"
+      markerWidth="0.5"
+      viewBox="0 0 1 1">
      <g
         id="inkstitch-guide-line-group">
        <path