Fix setting FxVersion headers by using constant (#46)

* Support deploying Windows container images.

* Check images string is not empty.

* Updated package version.

* Use constant when setting headers.

Author: chunye

packages/appservice-rest/package.json

@@ -1,6 +1,6 @@
 {
   "name": "azure-actions-appservice-rest",
-  "version": "1.3.2",
+  "version": "1.3.3",
   "description": "Azure resource manager and kudu node rest module",
   "keywords": [
     "appservice",

packages/appservice-rest/src/Utilities/KuduServiceUtility.ts

@@ -207,8 +207,7 @@ export class KuduServiceUtility {
                 throw 'The container image to be deployed to App Service is empty.';
             }
 
-            let fxVersionName = isLinux ? 'LinuxFxVersion' : 'WindowsFxVersion';
-            let headers = {fxVersionName: `DOCKER|${images}`};
+            let headers = isLinux ? { 'LinuxFxVersion': `DOCKER|${images}` } : { 'WindowsFxVersion': `DOCKER|${images}` };
             await this._webAppKuduService.imageDeploy(headers);
             console.log('Successfully deployed image to App Service.');
         }