style(theme): added slateorange theme (#588)

Co-authored-by: Anurag Hazra <hazru.anurag@gmail.com>

themes/index.js

@@ -251,6 +251,12 @@ const themes = {
     text_color: "27e8a7",
     bg_color: "242938"
   },
+  slateorange: {
+    title_color: "faa627",
+    icon_color: "faa627",
+    text_color: "ffffff",
+    bg_color: "36393f"
+  },
   kacho_ga: {
     title_color: "bf4a3f",
     icon_color: "a64833",