Add legend.linewidth to rcParam type hint

Author: rcomer

lib/matplotlib/typing.py

@@ -370,6 +370,7 @@
     "legend.handletextpad",
     "legend.labelcolor",
     "legend.labelspacing",
+    "legend.linewidth",
     "legend.loc",
     "legend.markerscale",
     "legend.numpoints",