Bump version to 1.3.1-alpha (#2067)

package-lock.json

@@ -1,6 +1,6 @@
 {
     "name": "vscode-docker",
-    "version": "1.3.0",
+    "version": "1.3.1-alpha",
     "lockfileVersion": 1,
     "requires": true,
     "dependencies": {

package.json

@@ -1,6 +1,6 @@
 {
     "name": "vscode-docker",
-    "version": "1.3.0",
+    "version": "1.3.1-alpha",
     "publisher": "ms-azuretools",
     "displayName": "Docker",
     "description": "Makes it easy to create, manage, and debug containerized applications.",