message: fix(theme): css filter breaking fixed position
  Add css filters to `html` instead of `body`
diff: @@ -15,11 +15,11 @@ export function setCssVar(prop: string, val: any, dom = document.documentElement
  dom.style.setProperty(prop, val);
  }
  -function toggleClass(flag: boolean, clsName: string) {
  - const body = document.body;
  - let { className } = body;
  +function toggleClass(flag: boolean, clsName: string, target?: HTMLElement) {
  + const targetEl = target || document.body;
  + let { className } = targetEl;
  className = className.replace(clsName, '');
  - document.body.className = flag ? `${className} ${clsName} ` : className;
  + targetEl.className = flag ? `${className} ${clsName} ` : className;
  }
  /**
  @@ -27,7 +27,7 @@ function toggleClass(flag: boolean, clsName: string) {
  * @param gray
  */
  export const updateColorWeak = (colorWeak: boolean) => {
  - toggleClass(colorWeak, 'color-weak');
  + toggleClass(colorWeak, 'color-weak', document.documentElement);
  };
  /**
  @@ -35,7 +35,7 @@ export const updateColorWeak = (colorWeak: boolean) => {
  * @param gray
  */
  export const updateGrayMode = (gray: boolean) => {
  - toggleClass(gray, 'gray-mode');
  + toggleClass(gray, 'gray-mode', document.documentElement);
  };
  /**
  