Add test for whitespace in doc alias

Author: GuillaumeGomez

src/test/rustdoc-js/doc-alias-whitespace.js

@@ -0,0 +1,19 @@
+// exact-check
+
+const QUERY = [
+    'Demon Lord',
+];
+
+const EXPECTED = [
+    {
+        'others': [
+            {
+                'path': 'doc_alias_whitespace',
+                'name': 'Struct',
+                'alias': 'Demon Lord',
+                'href': '../doc_alias_whitespace/struct.Struct.html',
+                'is_alias': true
+            },
+        ],
+    },
+];

src/test/rustdoc-js/doc-alias-whitespace.rs

@@ -0,0 +1,4 @@
+#![feature(doc_alias)]
+
+#[doc(alias = "Demon Lord")]
+pub struct Struct;