Revert "No additional properties (fixes microsoft/vscode-remote-release#2222)"

This reverts commit f643cad6e3.

extensions/configuration-editing/schemas/devContainer.schema.json

@@ -3,11 +3,9 @@
 	"description": "Defines a dev container",
 	"allowComments": true,
 	"type": "object",
-	"additionalProperties": false,
 	"definitions": {
 		"devContainerCommon": {
 			"type": "object",
-			"additionalProperties": false,
 			"properties": {
 				"name": {
 					"type": "string",
@@ -65,7 +63,6 @@
 		},
 		"nonComposeBase": {
 			"type": "object",
-			"additionalProperties": false,
 			"properties": {
 				"appPort": {
 					"type": [
@@ -134,7 +131,6 @@
 		},
 		"dockerFileContainer": {
 			"type": "object",
-			"additionalProperties": false,
 			"properties": {
 				"dockerFile": {
 					"type": "string",
@@ -151,7 +147,6 @@
 		},
 		"imageContainer": {
 			"type": "object",
-			"additionalProperties": false,
 			"properties": {
 				"image": {
 					"type": "string",
@@ -164,7 +159,6 @@
 		},
 		"composeContainer": {
 			"type": "object",
-			"additionalProperties": false,
 			"properties": {
 				"dockerComposeFile": {
 					"type": [