_sass: Add label classes for course modules

_sass/custom/mixins.scss

@@ -25,3 +25,8 @@
     margin: $sp-2 0;
   }
 }
+
+@mixin module-label() {
+  margin-left: 0;
+  padding-bottom: 0;
+}

_sass/custom/module.scss

@@ -78,3 +78,18 @@
     }
   }
 }
+
+.label.label-hw-out {
+  @extend .label-yellow;
+  @include module-label();
+}
+
+.label.label-hw-due {
+  @extend .label-red;
+  @include module-label();
+}
+
+.label.label-section {
+  @extend .label-purple;
+  @include module-label();
+}