add target "clean"

Makefile

@@ -3,6 +3,11 @@ PATCH_MEDIAELEMENT_PLUGINS=true
 
 .PHONY: \
     all \
+    clean \
+    clean-css \
+    clean-js \
+    clean-mediaelement \
+    clean-mediaelement-plugins \
     depend \
     depend-mediaelement \
     depend-mediaelement-plugins \
@@ -16,6 +21,24 @@ all: \
     css \
     src
 
+clean: \
+    clean-css \
+    clean-js \
+    clean-mediaelement \
+    clean-mediaelement-plugins
+
+clean-css:
+	rm -f dist/css/*.css dist/css/*.svg
+
+clean-js:
+	rm -f dist/js/*.js 
+
+clean-mediaelement:
+	git -C mediaelement reset --hard HEAD
+
+clean-mediaelement-plugins:
+	git -C mediaelement-plugins reset --hard HEAD
+
 depend: \
 	depend-node \
     depend-mediaelement \