add devcontainer-collection.json to npm bundle (microsoft/vscode-remote-containers#191)

Author: joshspicer

package.json

@@ -13,7 +13,8 @@
 		"containers-readmes",
 		"repository-containers",
 		"manifests",
-		"container-features"
+		"container-features",
+		"devcontainer-collection.json"
 	],
 	"scripts": {
 		"prepack": "rimraf containers-readmes manifests container-features && copyfiles --up 1 containers/**/README.md containers-readmes && copyfiles --up 1 containers/**/definition-manifest.json manifests && copyfiles --up 1 script-library/*.sh container-features && copyfiles --up 3 script-library/container-features/src/* container-features"