feat: Update AQI background colors to match airnow.gov (#589)

Author: foofoo

src/clock-weather-card.ts

@@ -509,12 +509,12 @@ export class ClockWeatherCard extends LitElement {
     if (aqi == null) {
       return null
     }
-    if (aqi <= 50) return 'green'
-    if (aqi <= 100) return 'yellowgreen'
-    if (aqi <= 150) return 'orange'
-    if (aqi <= 200) return 'red'
-    if (aqi <= 300) return 'purple'
-    return 'maroon'
+    if (aqi <= 50) return '#00FF00'
+    if (aqi <= 100) return '#FFFF00'
+    if (aqi <= 150) return '#FF8C00'
+    if (aqi <= 200) return '#FF0000'
+    if (aqi <= 300) return '#9400D3'
+    return '#8B0000'
   }
 
   private getSun (): HassEntityBase | undefined {