cli: allow js files to be processed by nodeTransform

Signed-off-by: MT Lewis <mtlewis@users.noreply.github.com>

.changeset/yellow-ducks-burn.md

@@ -0,0 +1,5 @@
+---
+'@backstage/cli': patch
+---
+
+Allow js files to be processed by the nodeTransform loader

packages/cli/config/nodeTransformHooks.mjs

@@ -127,10 +127,10 @@ async function withDetectedModuleType(resolved) {
     };
   }
 
-  // TODO(Rugvip): Afaik this should never happen and we can remove this check, but want it here for a little while to verify.
-  if (ext === '.js') {
-    throw new Error('Unexpected .js file without explicit format');
-  }
+  // Under normal circumstances .js files should reliably have a format and so
+  // we should only reach this point for .ts files. However, if additional
+  // custom loaders are being used the format may not be detected for .js files
+  // either. As such we don't restrict the file format at this point.
 
   // TODO(Rugvip): Does this need caching? kept it simple for now but worth exploring
   const packageJsonPath = await findPackageJSON(fileURLToPath(resolved.url));