Adding theme class name flag into #app

Signed-off-by: Alex Andreev <alex.andreev.email@gmail.com>

src/renderer/theme.store.ts

@@ -93,6 +93,9 @@ export class ThemeStore {
       return `--${cssName}: ${color} !important;`
     });
     this.styles.textContent = `:root {\n${cssVars.join("\n")}}`;
+    // Adding universal theme flag which can be used in component styles
+    const rootElem = document.getElementById("app");
+    rootElem.classList.toggle("theme-light", theme.type === ThemeType.LIGHT);
   }
 }