(docs) Add dark theme (#175)

.vscode/settings.json

@@ -5,6 +5,7 @@
         "MSIL",
         "Per's",
         "Waka",
-        "hljs"
+        "hljs",
+        "sidetoc"
     ]
 }

docs/docfx.json

@@ -70,10 +70,11 @@
               }
         },
 
-        // Our custom template changes are in docs/template
+        // Our custom template changes are in docs/templates/override
         "template": [
             "default",
-            "template"
+            "templates/override",
+            "templates/darkerfx"
         ],
 
         "postProcessors": [],

docs/templates/darkerfx/partials/affix.tmpl.partial

@@ -0,0 +1,39 @@
+{{!Copyright (c) Microsoft. All rights reserved. Licensed under the MIT license. See LICENSE file in the project root for full license information.}}
+
+<div class="hidden-sm col-md-2" role="complementary">
+  <div class="sideaffix">
+    {{^_disableContribution}}
+    <div class="contribution">
+      <ul class="nav">
+        {{#docurl}}
+        <li>
+          <a href="{{docurl}}" class="contribution-link">{{__global.improveThisDoc}}</a>
+        </li>
+        {{/docurl}}
+        {{#sourceurl}}
+        <li>
+          <a href="{{sourceurl}}" class="contribution-link">{{__global.viewSource}}</a>
+        </li>
+        {{/sourceurl}}
+      </ul>
+    </div>
+    {{/_disableContribution}}
+    <div class="toggle-mode">
+      <div class="icon">
+        <i aria-hidden="true">☀</i>
+      </div>
+      <label class="switch">
+        <input type="checkbox" id="switch-style">
+        <span class="slider round"></span>
+      </label>
+      <div class="icon">
+        <i aria-hidden="true">☾</i>
+      </div>
+      <script type="text/javascript" src="{{_rel}}styles/toggle-theme.js"></script>
+    </div>
+
+    <nav class="bs-docs-sidebar hidden-print hidden-xs hidden-sm affix" id="affix">
+    <!-- <p><a class="back-to-top" href="#top">Back to top</a><p> -->
+    </nav>
+  </div>
+</div>