Fix documentation search feature.

Via readthedocs/readthedocs.org#1088 (comment)

Author: rdadolf

docs/assets/fix_search.js

@@ -0,0 +1,23 @@
+$(document).ready(fixSearch);
+
+function fixSearch() {
+    var target = document.getElementById('rtd-search-form');
+    var config = {attributes: true, childList: true};
+
+    var observer = new MutationObserver(function(mutations) {
+      // if it isn't disconnected it'll loop infinitely because the observed element is modified
+      observer.disconnect();
+      var form = $('#rtd-search-form');
+      form.empty();
+      form.attr('action', 'https://' + window.location.hostname + '/en/' + determineSelectedBranch() + '/search.html');
+      $('<input>').attr({
+        type: "text",
+        name: "q",
+        placeholder: "Search docs"
+      }).appendTo(form);
+    });
+    // don't run this outside RTD hosting
+    if (window.location.origin.indexOf('readthedocs') > -1) {
+      observer.observe(target, config);
+    }
+  }

mkdocs.yml

@@ -6,6 +6,7 @@ google_analytics: ['UA-29492860-5', 'auto']
 theme: 'readthedocs'
 site_dir: 'deploy'
 extra_css: [assets/fathom.css]
+extra_js: [assets/fix_search.js]
 
 pages:
   - 'Overview': index.md