Add less linter via npx (#6936)

Author: xf-

.lesshintrc.json

@@ -0,0 +1,12 @@
+{
+  "idSelector": false,
+  "importPath": false,
+  "importantRule": false,
+  "maxCharPerLine": false,
+  "propertyOrdering": false,
+  "qualifyingElement": false,
+  "spaceAroundComma": false,
+  "stringQuotes": "double",
+  "universalSelector": false,
+  "zeroUnit": "no_unit"
+}

Makefile

@@ -388,6 +388,7 @@ generate-stylesheets:
 		exit 1; \
 	fi;
 	$(eval BROWSERS := "> 1%, last 2 firefox versions, last 2 safari versions, ie 11")
+	npx lesshint  public/less/
 	npx lessc --clean-css="--s0 -b" public/less/index.less public/css/index.css
 	$(foreach file, $(filter-out public/less/themes/_base.less, $(wildcard public/less/themes/*)),npx lessc --clean-css="--s0 -b" public/less/themes/$(notdir $(file)) > public/css/theme-$(notdir $(call strip-suffix,$(file))).css;)
 	$(foreach file, $(wildcard public/css/*),npx postcss --use autoprefixer --autoprefixer.browsers $(BROWSERS) -o $(file) $(file);)