[matrix] Create settings modal

* Create settings modal

* Fix issue with spacing after settings button

* Fix issue with modal background on mobile devices

* Add close button to modal

* Add tooltip to close button

* Support closing modal with escape key

* Add missing semicolon to keydown event listener

docs/_static/style.css

@@ -1,7 +1,5 @@
 /* this stuff uses a couple of themes as a base with some custom stuff added
-
 In particular thanks to:
-
 - Alabaster for being a good base
   - Which thanks Flask + KR theme
 - Sphinx Readable Theme
@@ -58,6 +56,43 @@ div.footer a {
   text-decoration: underline;
 }
 
+div.modal {
+  position: fixed;
+  z-index: 1;
+  left: 0;
+  top: 0;
+  width: 100%;
+  height: 100%;
+  overflow: auto;
+  background-color: rgba(0,0,0,0.4);
+  cursor: pointer;
+}
+
+div.modal-content {
+  background-color: #ffffff;
+  box-shadow: 0 2px 8px rgba(0,0,0,0.54);
+  padding: 24px;
+  border-radius: 4px;
+  margin: 20% auto;
+  width: 40%;
+  cursor: initial;
+}
+
+div.modal-content > span.close {
+  color: #888;
+  float: right;
+  font-size: 24px;
+  font-weight: bold;
+  cursor: pointer;
+  -moz-user-select: none;
+  -webkit-user-select: none;
+}
+
+div.modal-content > span.close:hover,
+div.modal-content > span.close:focus {
+  color: #444;
+}
+
 div.related {
   padding: 10px 10px;
   width: 100%;
@@ -617,4 +652,4 @@ div.code-block-caption {
     background-color: transparent;
     border-left: none;
   }
-}
+}