build: properly inline multiple styles (#4911)

* Recently we moved the inline script to the packaging directory and we cleaned up some logic. At this point the multiple style files inlining broke accidentally.
* We joined the different styles using a comma inside of the inlined stylesheet (while we were trying to create a array). Instead it would be just easier to concatenate the styles using a space.

tools/gulp/packaging/inline-resources.ts

@@ -40,7 +40,7 @@ function inlineStyles(fileContent: string, filePath: string) {
       .map(url => join(dirname(filePath), url))
       .map(path => loadResourceFile(path));
 
-    return `styles: ["${styleContents.join(',')}"]`;
+    return `styles: ["${styleContents.join(' ')}"]`;
   });
 }