fix: workingDirectory props was not used (#58)

## Change Description

Change to use workingDirectory props.

## Why need this change?

Currently, NodejsBuild accept to specification workingDirectory for
props. However, the value was not used.

## Possible breaking change

Users who have been using `workingDirectory` property might see
unexpected behavior after the upgrade. To get back the previous
behavior, they can just remove the `workingDirectory` property, because
it was not used at all previously.

---------

Co-authored-by: Masashi Tomooka <[email protected]>

Author: WinterYukky

src/nodejs-build.ts

@@ -275,16 +275,17 @@ curl -i -X PUT -H 'Content-Type:' -d "@payload.json" "$responseURL"
       commands: s.commands,
     }));
 
+    const workingDirectory = props.workingDirectory ?? sources[0].extractPath;
     const properties: NodejsBuildResourceProps = {
       type: 'NodejsBuild',
       sources,
       destinationBucketName: props.destinationBucket.bucketName,
       destinationKeyPrefix: props.destinationKeyPrefix ?? '/',
       distributionId: props.distribution?.distributionId,
       assetBucketName: bucket.bucketName,
-      workingDirectory: sources[0].extractPath,
+      workingDirectory,
       // join paths for CodeBuild (Linux) platform
-      outputSourceDirectory: posix.join(sources[0].extractPath, props.outputSourceDirectory),
+      outputSourceDirectory: posix.join(workingDirectory, props.outputSourceDirectory),
       environment: props.buildEnvironment,
       buildCommands: props.buildCommands ?? ['npm run build'],
       codeBuildProjectName: project.projectName,