style: tweaks

- made hero h1 black
- fixed the styles of lesson teasers

community/public/css/style.less

@@ -288,3 +288,17 @@ section.lightgray {
     font-weight: bold;
   }
 }
+
+.chapter-description {
+  margin-bottom: 10px;
+}
+
+.lesson-teaser {
+  font-weight: bold;
+  color: black;
+  padding-left: 20px;
+}
+
+#hero h1 {
+  color: black !important;
+}