enhance: move background color from body to html to enable developer override (#6364)

chore: all override background

Author: zombieJ

src/global/global.less

@@ -3,13 +3,17 @@
 
 :root {
   -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
+  --adm-color-background-body: var(--adm-color-background);
+}
+
+html {
+  background-color: var(--adm-color-background-body);
 }
 
 body {
   color: var(--adm-color-text);
   font-size: var(--adm-font-size-main);
   font-family: var(--adm-font-family);
-  background-color: var(--adm-color-background);
 }
 
 a,