Improve no result found sentence in doc search

Author: GuillaumeGomez

src/librustdoc/html/static/main.js

@@ -1340,7 +1340,16 @@
                 output = '<div class="search-failed"' + extraStyle + '>No results :(<br/>' +
                     'Try on <a href="https://duckduckgo.com/?q=' +
                     encodeURIComponent('rust ' + query.query) +
-                    '">DuckDuckGo</a>?</div>';
+                    '">DuckDuckGo</a>?<br/><br/>' +
+                    'Or try looking in one of these:<ul><li>The <a ' +
+                    'href="https://doc.rust-lang.org/reference/index.html">Rust Reference</a> for' +
+                    ' technical details about the language.</li><li><a ' +
+                    'href="https://doc.rust-lang.org/rust-by-example/index.html">Rust By Example' +
+                    '</a> for expository code examples.</a></li><li>The <a ' +
+                    'href="https://doc.rust-lang.org/book/index.html">Rust Book</a> for ' +
+                    'introductions to language features and the language itself.</li><li><a ' +
+                    'href="https://docs.rs">Docs.rs</a> for documentation of crates released on ' +
+                    '<a href="https://crates.io/">crates.io</a>.</li></ul></div>';
             }
             return [output, length];
         }

src/librustdoc/html/static/rustdoc.css

@@ -658,9 +658,9 @@ a {
 	padding-right: 10px;
 }
 .content .search-results td:first-child a:after {
-    clear: both;
-    content: "";
-    display: block;
+	clear: both;
+	content: "";
+	display: block;
 }
 .content .search-results td:first-child a span {
 	float: left;
@@ -1116,6 +1116,13 @@ pre.rust {
 	margin-top: 20px;
 }
 
+.search-failed > ul {
+	text-align: left;
+	max-width: 570px;
+	margin-left: auto;
+	margin-right: auto;
+}
+
 #titles {
 	height: 35px;
 }

src/librustdoc/html/static/themes/dark.css

@@ -285,7 +285,7 @@ pre.ignore:hover, .information:hover + pre.ignore {
 	color: rgba(255,142,0,1);
 }
 
-.search-failed > a {
+.search-failed a {
 	color: #0089ff;
 }
 

src/librustdoc/html/static/themes/light.css

@@ -279,7 +279,7 @@ pre.ignore:hover, .information:hover + pre.ignore {
 	color: rgba(255,142,0,1);
 }
 
-.search-failed > a {
+.search-failed a {
 	color: #0089ff;
 }