Improve concats.js, scripts.js, svgs.js

Added:
- Condition to cast `includes` into an array.

Removed:
- Variable `files` in favour of reusing `includes` in 'concats.js'.

build/tasks/svgs.js

@@ -60,6 +60,10 @@ export default async function compileSVGs(mixerOptions = null) {
         console.time(timeLabel);
 
         try {
+            if (!Array.isArray(includes)) {
+                includes = [ includes ];
+            }
+
             includes = resolve(includes);
             outfile  = resolve(outfile);