refactor: use postcss-values-parser for @import at rule (#4435)

* update to postcss value parser for @import and at rule

* fix specs

* Add rule for @import url and fix specs

* fix more specs

* fix more specs

* import check

* fix specs and add more specs

* remove console.log

* review fixes

* update snapshots

* remove bad code

* fix spec

* remove code

* Add comment

* fix comment

* lint fix

src/language-css/parser-postcss.js

@@ -366,7 +366,7 @@ function parseNestedCSS(node) {
 
       if (name === "at-root") {
         if (/^\(\s*(without|with)\s*:[\s\S]+\)$/.test(params)) {
-          node.params = parseMediaQuery(params);
+          node.params = parseValue(params);
         } else {
           node.selector = parseSelector(params);
           delete node.params;
@@ -375,6 +375,11 @@ function parseNestedCSS(node) {
         return node;
       }
 
+      if (lowercasedName === "import") {
+        node.params = parseValue(params);
+        return node;
+      }
+
       if (
         [
           "namespace",
@@ -414,7 +419,7 @@ function parseNestedCSS(node) {
         return node;
       }
 
-      if (["import", "media", "custom-media"].indexOf(lowercasedName) !== -1) {
+      if (["media", "custom-media"].indexOf(lowercasedName) !== -1) {
         if (params.includes("#{")) {
           // Workaround for media at rule with scss interpolation
           return {