add reload button the changelog

Author: Chilipp

CHANGELOG.rst

@@ -12,4 +12,7 @@ Changed
 Added
 -----
 - A widget to control the plot type for mapplot and plot2d (see
-  `#46 <https://github.com/psyplot/psy-view/pull/46>`__)
+  `#46 <https://github.com/psyplot/psy-view/pull/46>`__)
+- A button to reload all plots. This is useful, for instance, if the data on
+  your disk changed and you just want to update the plot
+  `#48 <https://github.com/psyplot/psy-view/pull/48>`__)