Move css config to TS

src/css_composer/config/config.js

@@ -1,7 +0,0 @@
-export default {
-  // Style prefix
-  stylePrefix: 'css-',
-
-  // Default CSS style
-  rules: [],
-};

src/css_composer/config/config.ts

@@ -0,0 +1,19 @@
+export interface CssComposerConfig {
+  /**
+   * Style prefix.
+   * @default 'css-'
+   */
+  stylePrefix?: string;
+
+  /**
+   * Default CSS style rules
+   */
+  rules?: Array<string>; // TODO
+}
+
+const config: CssComposerConfig = {
+  stylePrefix: 'css-',
+  rules: [],
+};
+
+export default config;