Fix svg text alignment for "middle"

See https://stackoverflow.com/questions/19212498/firefox-support-for-alignment-baseline-property/21373135#21373135

boxes/__init__.py

@@ -361,10 +361,10 @@ class Boxes:
             self.ctx.rectangle(0, 0, self.reference, 10)
             if self.reference < 40:
                 self.text("%.fmm" % self.reference, self.reference + 5, 5,
-                          align="middle left")
+                          align="middle left", fontsize=8, color=Color.ETCHING)
             else:
                 self.text("%.fmm" % self.reference, self.reference / 2.0, 5,
-                          align="middle center")
+                          align="middle center", fontsize=8, color=Color.ETCHING)
             self.move(10, 10, "up")
             self.ctx.stroke()
 

boxes/drawing.py

@@ -546,7 +546,7 @@ Creation date: {date}
                         t.text = text
                         t.set("font-size", f"{params['fs']}px")
                         t.set("text-anchor", params.get('align', 'left'))
-                        t.set("alignment-baseline", 'hanging')
+                        t.set("dominant-baseline", 'hanging')
                     else:
                         print("Unknown", c)