fix(index): use path.posix for platform consistency

src/index.js

@@ -19,7 +19,7 @@ export default function loader(content) {
   });
 
   let outputPath = (
-    typeof options.outputPath === 'function' ? options.outputPath(url) : path.join(options.outputPath || '', url)
+    typeof options.outputPath === 'function' ? options.outputPath(url) : path.posix.join(options.outputPath || '', url)
   );
 
   if (options.useRelativePath) {
@@ -32,9 +32,9 @@ export default function loader(content) {
     const relativePath = relativeUrl && `${path.dirname(relativeUrl)}/`;
     // eslint-disable-next-line no-bitwise
     if (~relativePath.indexOf('../')) {
-      outputPath = path.join(outputPath, relativePath, url);
+      outputPath = path.posix.join(outputPath, relativePath, url);
     } else {
-      outputPath = path.join(relativePath, url);
+      outputPath = path.posix.join(relativePath, url);
     }
   }
 
@@ -43,7 +43,7 @@ export default function loader(content) {
   if (options.publicPath !== undefined) {
     // support functions as publicPath to generate them dynamically
     publicPath = JSON.stringify(
-      typeof options.publicPath === 'function' ? options.publicPath(url) : path.join(options.publicPath || '', url),
+      typeof options.publicPath === 'function' ? options.publicPath(url) : path.posix.join(options.publicPath || '', url),
     );
   } else {
     publicPath = `__webpack_public_path__ + ${JSON.stringify(outputPath)}`;