add new line to release code to change the mu plugin version (#33)

Co-authored-by: Joe Worthington <joe@pie.co.de>

Author: Joseph-Worthington

.github/workflows/release.yml

@@ -61,6 +61,7 @@ jobs:
             sed -i "s/version\":\ \"[0-9]\+\.\?[0-9]*\.\?[0-9]*/version\":\ \"${{ needs.check_for_release.outputs.version }}/g" ./update.json
             sed -i "s/download\/[0-9]\+\.\?[0-9]*\.\?[0-9]*/download\/${{ needs.check_for_release.outputs.version }}/g" ./update.json
             sed -i "s/Version:\ [0-9]\+\.\?[0-9]*\.\?[0-9]*/Version:\ ${{ needs.check_for_release.outputs.version }}/g" ./${{ github.event.repository.name }}.php
+            sed -i "s/Version:\ [0-9]\+\.\?[0-9]*\.\?[0-9]*/Version:\ ${{ needs.check_for_release.outputs.version }}/g" ./${{ github.event.repository.name }}-mu.php
             sed -i "s/\[Unreleased\]/\[Unreleased\]\r\n\r\n## \[${{ needs.check_for_release.outputs.version }}\] ${{steps.get_date.outputs.date}} /g" ./changelog.md
             git config user.name "Github Actions"
             git config user.email "<>"