search: add pre tags to algolia search

Author: jslvtr

docs/algolia.config.json

@@ -23,7 +23,7 @@
         "lvl4": "article h4",
         "lvl5": "article h5, article td:first-child",
         "lvl6": "article h6",
-        "text": "article p, article li, article td:last-child"
+        "text": "article p, article pre, article li, article td:last-child"
     },
     "strip_chars": " .,;:#",
     "custom_settings": {