[MXNET-356] Fix for the search results issues (apache#10656)

* Fix for the search results issues. This changes reads the current version (if it exists) to add it as a part of the URL given in the search results drop-down. Next, in the search results page corrected the search preview target page from txt to html

* Changing the AJAX type from html back to txt

* Fixing the broken changes in the searchtools js

docs/_static/searchtools_custom.js

@@ -458,6 +458,16 @@ var Search = {
             } else {
                 // normal html builders
                 var baseURL = 'https://' + window.location.hostname + '/';
+                var urlHref = window.location.href;
+                let urlSplits = urlHref.split("/");
+                let versionString = '';
+                for (var idx = 0; idx < urlSplits.length; ++idx) {
+                    if(urlSplits[idx] == 'versions') {
+                        versionString = 'versions/' + urlSplits[idx + 1] + '/';
+                        break;
+                    }
+                }
+                baseURL = baseURL.concat(versionString);
                 listItem.append($('<a/>').attr('href',
                 baseURL + item[0] + DOCUMENTATION_OPTIONS.FILE_SUFFIX +
                 highlightstring + item[2]).html(item[1]));