Make it posible to customize nav text color via css var (#26807)

---
*Sponsored by Kithara Software GmbH*

Author: 6543

web_src/css/base.css

@@ -245,6 +245,7 @@
   --color-tooltip-bg: #000000f0;
   --color-nav-bg: #ffffff;
   --color-nav-hover-bg: #ebebeb;
+  --color-nav-text: var(--color-text);
   --color-label-text: #232323;
   --color-label-bg: #cacaca5b;
   --color-label-hover-bg: #cacacaa0;

web_src/css/modules/navbar.css

@@ -34,6 +34,10 @@
   justify-content: center;
 }
 
+#navbar > .menu > .item {
+  color: var(--color-nav-text);
+}
+
 #navbar .dropdown .item {
   justify-content: stretch;
 }