Fix S3 download mkdirp folders instead of writeStream (#482)

## Description
I added directory detection with slash ending, separated the directory keys creation to use mkdirp and preserved the current logic for files.

## Motivation
the S3 download task failed to create nested objects after creating base directories as 0 byte files.

## Related Issue(s)
#480
#468

Author: motisoft

.changes/next-release/Bug Fix-8563f281-45a1-430b-999f-9a70940dc983.json

@@ -0,0 +1,4 @@
+{
+	"type": "Bug Fix",
+	"description": "S3Download now correctly handles directories"
+}

src/tasks/S3Download/TaskOperations.ts

@@ -82,20 +82,28 @@ export class TaskOperations {
 
     private async downloadFile(s3Params: S3.GetObjectRequest, dest: string): Promise<void> {
         return new Promise<void>((resolve, reject) => {
-            const dir: string = path.dirname(dest)
-            if (!fs.existsSync(dir)) {
-                tl.mkdirP(dir)
+            const isDir = dest.endsWith('/')
+            if (isDir) {
+                this.createDirectory(dest)
+            } else {
+                const dir: string = path.dirname(dest)
+                this.createDirectory(dir)
+                const file = fs.createWriteStream(dest)
+                const s3Stream = this.s3Client.getObject(s3Params).createReadStream()
+                s3Stream.on('error', reject)
+                file.on('error', reject)
+                file.on('close', resolve)
+                s3Stream.pipe(file)
             }
-
-            const file = fs.createWriteStream(dest)
-            const s3Stream = this.s3Client.getObject(s3Params).createReadStream()
-            s3Stream.on('error', reject)
-            file.on('error', reject)
-            file.on('close', resolve)
-            s3Stream.pipe(file)
         })
     }
 
+    private createDirectory(path: string) {
+        if (!fs.existsSync(path)) {
+            tl.mkdirP(path)
+        }
+    }
+
     private async fetchAllObjectKeys(): Promise<string[]> {
         if (this.taskParameters.sourceFolder) {
             console.log(