Run replace function on intro page as well

builder.js

@@ -101,15 +101,19 @@ export class Builder {
         ({name, data}) => ([name, data])
       )
     )
+    const replace = this.buildReplace(filesMap)
     const intro = this.buildModule({
       name: '_intro.js',
-      data: (
-        '_intro.js' in filesMap ? 
-        filesMap['_intro.js'] :
-        defaultIntro
-      ),
+      data: replace({
+        name: '_intro.js',
+        data: (
+          '_intro.js' in filesMap ? 
+          filesMap['_intro.js'] :
+          defaultIntro
+        ),
+        files: this.files,
+      })
     })
-    const replace = this.buildReplace(filesMap)
     const modules = this.files.filter(({name}) => (
       name.endsWith('.js') && 
       !name.startsWith('_')