feat: add-task usability improvements (#2767)

Co-authored-by: Dominik Pschenitschni <mail@celement.de>
Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/2767
Reviewed-by: konrad <k@knt.li>
Co-authored-by: Dominik Pschenitschni <dpschen@noreply.kolaente.de>
Co-committed-by: Dominik Pschenitschni <dpschen@noreply.kolaente.de>

src/helpers/getInheritedBackgroundColor.ts

@@ -0,0 +1,24 @@
+function getDefaultBackground() {
+  const div = document.createElement('div')
+  document.head.appendChild(div)
+  const bg = window.getComputedStyle(div).backgroundColor
+  document.head.removeChild(div)
+  return bg
+}
+
+// get default style for current browser
+const defaultStyle = getDefaultBackground() // typically "rgba(0, 0, 0, 0)"
+
+// based on https://stackoverflow.com/a/62630563/15522256
+export function getInheritedBackgroundColor(el: HTMLElement): string {  
+  const backgroundColor = window.getComputedStyle(el).backgroundColor
+
+  if (backgroundColor !== defaultStyle) return backgroundColor
+
+  if (!el.parentElement) {
+		// we reached the top parent el without getting an explicit color
+		return defaultStyle
+	}
+  
+  return getInheritedBackgroundColor(el.parentElement)
+}