Add new option customTypings

Closes #19

Author: c0gnize

README.md

@@ -60,6 +60,20 @@ export = styles;
 ### `banner`
 Adds a "banner" prefix to each generated file.
 
+### `customTypings`
+A function that accepts classes (an array of string) and returns the content of declaration file:
+```js
+customTypings: classes => {
+  let content = '// This file is generated automatically\ndeclare const styles: {\n';
+  for (const c of classes) {
+    content += `  ${c}: string;\n`;
+  }
+  content += '};\nexport default styles;\n';
+  return content;
+}
+```
+`namedExport` option will be ignored
+
 ## Usage in Typescript
 ```ts
 import * as styles from './_button.scss';

index.js

@@ -7,6 +7,7 @@ const loaderUtils = require('loader-utils');
 module.exports = function(content) {
   this.cacheable && this.cacheable();
 
+  /** @type {{ banner?: string, namedExport?: boolean, customTypings?: (classes: string[]) => string }} */
   const options = loaderUtils.getOptions(this) || {};
   const callback = this.async();
 
@@ -18,7 +19,9 @@ module.exports = function(content) {
 
   {
     const classes = getClasses(content);
-    if (options.namedExport) {
+    if (options.customTypings) {
+      typings = options.customTypings(classes);
+    } else if (options.namedExport) {
       for (let c of classes) {
         typings += `export const ${c}: string;\n`;
       }

package.json

@@ -1,6 +1,6 @@
 {
   "name": "dts-css-modules-loader",
-  "version": "1.0.4",
+  "version": "1.1.0",
   "description": "webpack loader to generate typings for css modules",
   "dependencies": {
     "loader-utils": "^2.0.0"