Fix handlebars path issue on Windows OS.

server.js

@@ -77,7 +77,7 @@ app.get('/', async (req, res) => {
 
   data.helpers = {
     port,
-    include_partial: (filesPath) => path.join(modulesPath, filesPath),
+    include_partial: (filesPath) => handlebarLayoutsPath(modulesPath, filesPath),
     baseView,
     previewFrameUrl: `${previewFrameUrl}/${baseViewUrl}`,
   }
@@ -95,8 +95,8 @@ app.get('/view/:baseView', async (req, res) => {
   const blockName = config.has('blockName') ? config.get('blockName') : developmentBlockName;
 
   data.helpers = {
-    include_partial: (filesPath) => path.join(modulesPath, filesPath),
-    include_block_template: () => path.join(projectPath, 'src', `${blockName}.template`),
+    include_partial: (filesPath) => handlebarLayoutsPath(modulesPath, filesPath),
+    include_block_template: () => handlebarLayoutsPath(projectPath, 'src', `${blockName}.template`),
     section_class: `${blockName}--${jsonFileName}`,
     base_url: '/'
   }
@@ -396,3 +396,8 @@ function handleSyntaxErrors(err, req, res, next) {
 
   next();
 }
+
+function handlebarLayoutsPath() {
+  return path.join(...arguments)
+    .replace(/\\/g, '/'); // Windows path issue. Fix all "\" for Handlebars.
+}