docs: change color brand-soft

Author: hywax

docs/.vitepress/theme/custom.css

@@ -2,5 +2,5 @@
   --vp-c-brand-1: #91c198;
   --vp-c-brand-2: #7cb484;
   --vp-c-brand-3: #609966;
-  --vp-c-brand-soft: #eaf4ec;
+  --vp-c-brand-soft: rgb(100 255 170 / 16%);
 }