add step to release checklist

DEVELOP.md

@@ -126,6 +126,7 @@ Before creating a new release, make sure to complete the following checklist:
 - [ ] Bump the version in the [metadata.txt](https://github.com/GIS4WRF/gis4wrf/blob/master/gis4wrf/metadata.txt) file.
 - [ ] Check that all issues and PRs for the version number to release have been closed.
 - [ ] [Create the zip package](https://github.com/GIS4WRF/gis4wrf/blob/master/DEVELOP.md#zip-packaging).
+- [ ] Test the zip package locally.
 - [ ] Upload the zip package to the [QGIS Python Plugins Repository](https://plugins.qgis.org).
 - [ ] Tag a new release.
 - [ ] Close the issue named `Prepare for GIS4WRF <VERSION_NUMBER> release`.