Docs: Enable RTD on tf-m-tests

Added files required for the tf-m-tests documentation to be displayed on Read the Docs

Change-Id: I073fb19e106eb1c218ebc9fda43cec0aa20c39cf
Signed-off-by: Elena Uziunaite <elena.uziunaite@arm.com>
diff --git a/docs/_static/css/tfm_custom.css b/docs/_static/css/tfm_custom.css
new file mode 100644
index 0000000..dfc4e55
--- /dev/null
+++ b/docs/_static/css/tfm_custom.css
@@ -0,0 +1,82 @@
+/*-----------------------------------------------------------------------------
+# Copyright (c) 2020, Arm Limited. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+#----------------------------------------------------------------------------*/
+
+/* Override table no-wrap */
+.wy-table-responsive table td, .wy-table-responsive table th {
+    white-space: normal;
+}
+
+/* Limit page width */
+@media only screen and (min-width: 780px) {
+    .wy-nav-content {
+        max-width: 1100px;
+    }
+}
+
+/* Flexbox Tile Grid Settings  */
+.grid {
+    list-style-type: none !important;
+    display: -webkit-box;
+    display: -ms-flexbox;
+    display: flex;
+    -ms-flex-wrap: wrap;
+        flex-wrap: wrap;
+    -webkit-box-pack: center;
+        -ms-flex-pack: center;
+            justify-content: center;
+    margin: 1rem auto;
+    max-width: calc((250px + 2rem) * 4);
+}
+
+.grid-item {
+    list-style-type: none !important;
+    -webkit-box-flex: 0;
+        -ms-flex: 0 0 auto;
+            flex: 0 0 auto;
+    width: 200px;
+    text-align: center;
+    margin: 1rem;
+}
+
+.grid-item a {
+    display: block;
+    width: 190px;
+    height: 190px;
+    padding: 12px;
+    display: -webkit-box;
+    display: -ms-flexbox;
+    display: flex;
+    -webkit-box-orient: vertical;
+    -webkit-box-direction: normal;
+        -ms-flex-direction: column;
+            flex-direction: column;
+    -webkit-box-pack: center;
+        -ms-flex-pack: center;
+            justify-content: center;
+    -webkit-box-align: center;
+        -ms-flex-align: center;
+            align-items: center;
+    border: 1px solid #c6cbce;
+    background-color: #2980B9;
+    color: white;
+}
+
+.grid-item h2 {
+    font-size: 1rem;
+    margin-bottom: 0.5rem;
+}
+
+.grid-item img {
+    max-width: 75%;
+    margin-bottom: 0.5rem;
+}
+
+
+.grid-item a:hover {
+    background-color: #32cd32;
+    color: white;
+}