expanded the breakpoints definition

Author: geelen

test/test-cases/constants/breakpoints.css

@@ -1 +1,3 @@
-@let small: (max-width: 599px);
+@let small (max-width: 599px);
+@let medium (min-width: 600px) and (max-width: 959px);
+@let large (min-width: 960px);

test/test-cases/constants/expected.css

@@ -13,3 +13,8 @@
     background: white;
   }
 }
+@media (min-width: 600px) and (max-width: 959px) {
+  ._constants_source__foo {
+    background: peru;
+  }
+}

test/test-cases/constants/source.css

@@ -1,5 +1,5 @@
 @let borders: "./borders.css", breakpoints: "./breakpoints.css";
-@-import small from breakpoints;
+@-import small, medium from breakpoints;
 @import secondary, primary as blue from "./colors.css";
 
 .foo {
@@ -13,3 +13,8 @@
     background: white;
   }
 }
+@media medium {
+  .foo {
+    background: peru;
+  }
+}