Fix flow issues

Author: rlamacraft

src/main/webapp/ui/flow-typed/mui.js

@@ -24,6 +24,14 @@ declare module "@mui/system" {
    */
   declare export function darken(color: string, coefficient: number): string;
 
+  /**
+   * Lightens a color.
+   * @param {string} color - CSS color, i.e. one of: #nnn, #nnnnnn, rgb(), rgba(), hsl(), hsla(), color()
+   * @param {number} coefficient - multiplier in the range 0 - 1
+   * @returns {string} A CSS color string. Hex input values are returned as rgb
+   */
+  declare export function lighten(color: string, coefficient: number): string;
+
   /**
    * Applies a transparency to a color.
    * @param {string} color - CSS color, i.e. one of: #nnn, #nnnnnn, rgb(), rgba(), hsl(), hsla(), color()