Add new "Deep Blue" dark theme (#8015)

Author: moolbie

newIDE/app/src/UI/Theme/DeepBlueTheme/index.js

@@ -0,0 +1,12 @@
+import { createGdevelopTheme } from '../CreateTheme';
+
+import styles from './DeepBlueThemeVariables.json';
+import './DeepBlueThemeVariables.css';
+
+export default createGdevelopTheme({
+  styles,
+
+  rootClassNameIdentifier: 'DeepBlueTheme',
+  paletteType: 'dark',
+  gdevelopIconsCSSFilter: 'hue-rotate(-10deg) saturate(50%)',
+});