Allow processing of @container at-rule, add tests for it

Author: Vlad Yelahin

index.js

@@ -210,6 +210,10 @@ const factory = ({
           // eslint-disable-next-line no-param-reassign
           node.params = replaceValueSymbols(node.params, definitions);
         },
+        container(node) {
+          // eslint-disable-next-line no-param-reassign
+          node.params = replaceValueSymbols(node.params, definitions);
+        },
         value(node) {
           if (noEmitExports) {
             node.remove();

index.test.js

@@ -271,6 +271,14 @@ test('should replace inside media queries', async (t) => {
   );
 });
 
+test('should replace inside container queries', async (t) => {
+  await run(
+    t,
+    '@value base: 10px;\n@container (min-width: calc(base * 200)) {}',
+    '@value base: 10px;\n@container (min-width: calc(10px * 200)) {}',
+  );
+});
+
 test('should allow custom-property-style names', async (t) => {
   await run(
     t,