feat(blazorui): improve theme colors of BlazorUI #10729 (#10753)

Author: msynk

src/BlazorUI/Bit.BlazorUI/Styles/Fluent/colors.fluent-dark.scss

@@ -99,7 +99,7 @@
     --bit-clr-fg-ter: #616973;
     --bit-clr-fg-ter-hover: #565D66;
     --bit-clr-fg-ter-active: #4B5159;
-    --bit-clr-fg-dis: #343b42;
+    --bit-clr-fg-dis: #666;
     //backgrounds
     --bit-clr-bg-pri: #010409;
     --bit-clr-bg-pri-hover: #0E141B;

src/BlazorUI/Bit.BlazorUI/Styles/Fluent/colors.fluent-light.scss

@@ -106,7 +106,7 @@
     --bit-clr-bg-pri: #FFF;
     --bit-clr-bg-pri-hover: #F2F2F2;
     --bit-clr-bg-pri-active: #EBEBEB;
-    --bit-clr-bg-sec: #FAF9F8;
+    --bit-clr-bg-sec: #F5F5F5;
     --bit-clr-bg-sec-hover: #F2F1F0;
     --bit-clr-bg-sec-active: #E8E7E6;
     --bit-clr-bg-ter: #EDECEB;