Wrap Build Encyclopedia rule signatures.

--
MOS_MIGRATED_REVID=121706420
diff --git a/site/_sass/style.scss b/site/_sass/style.scss
index 6da9d87..01f71c4 100644
--- a/site/_sass/style.scss
+++ b/site/_sass/style.scss
@@ -385,6 +385,14 @@
   }
 }
 
+// Build Encyclopedia and Skylark Library
+
+pre.rule-signature {
+  white-space: normal;
+  word-wrap: break-word;
+  word-break: normal;
+}
+
 colgroup {
   .col-param {
     width: 25%;