CSS: Restrict readme image width

Fixes #971

Author: anthonynguyen

app/styles/crate.scss

@@ -306,6 +306,10 @@
     .crate-readme {
         line-height: 1.5;
 
+        img {
+            max-width: 100%;
+        }
+
         pre {
             overflow-x: scroll;
         }