Fix broken search bar in docs site (#1135)

* Fixes for search on docs site

We previously didn't include the search results page in our CI testing,
so we missed some issues on that page. This ensures that page is part of
regular testing, and also includes fixes for the issues present.

* fix sidebar contrast

docs_theme/search.html

@@ -0,0 +1,29 @@
+{% extends "main.html" %}
+
+{% block content %}
+
+<div role="search">
+  <form id ="content_search" class="wy-form mkdocs-search" action="{{ base_url }}/search.html" method="get">
+
+    <span role="status" aria-live="polite" class="ui-helper-hidden-accessible"></span>
+    <input
+      name="q"
+      id="mkdocs-search-query"
+      type="text"
+      class="search_input search-query ui-autocomplete-input"
+      placeholder="Search the Docs"
+      autocomplete="off"
+      autofocus
+      title="Type search term here"
+    >
+    <button class="icon icon-search" aria-label="submit"></button>
+  </form>
+</div>
+
+  <h1 id="search">Results</h1>
+
+  <div id="mkdocs-search-results" class="search-results">
+    Searching...
+  </div>
+
+{% endblock %}