Docs: Use doxygen-awesome-css theme (#6512)

* add doxygen-theme-css submodule

* enable theme and disable not needed code references

* hide nav sync button

* css and cleanup

* Move comments to dedicated README to not fail config check

doc/doxygen/css/cockatrice_docs_style.css

@@ -0,0 +1,33 @@
+/*
+
+See "Awesome Doxygen CSS" theme docs:
+https://jothepro.github.io/doxygen-awesome-css/md_docs_2customization.html#autotoc_md36
+
+Adjustments here are based on the css file of the theme and variables defined there.
+
+*/
+
+
+/* Light Mode overrides */
+html {
+    --primary-color: #33a946;
+    --primary-dark-color: #33a946;
+    --primary-light-color: #33a946;
+}
+
+/* Dark Mode overrides */
+@media (prefers-color-scheme: dark) {
+    html:not(.light-mode) {
+        --primary-color: #33a946;
+        --primary-dark-color: #33a946;
+        --primary-light-color: #33a946;
+    }
+}
+
+/* Dark Mode overrides, defined twice to support both the dark-mode without and with doxygen-awesome-darkmode-toggle.js */
+html.dark-mode {
+    color-scheme: dark;
+    --primary-color: #33a946;
+    --primary-dark-color: #33a946;
+    --primary-light-color: #33a946;
+}

doc/doxygen/css/hide_nav_sync.css

@@ -0,0 +1,10 @@
+/* hide navigation sync control and icons */
+#nav-sync,
+#nav-sync * {
+    display: none !important;
+}
+
+div.nav-sync-icon,
+div.nav-sync-icon * {
+    display: none !important;
+}