Revert "No need for package.json main": needed by codesandbox.io

This reverts commit ab0b86f.

Author: tkrotoff

examples/Bootstrap4/package.json

@@ -11,6 +11,7 @@
     "bootstrap",
     "bootstrap4"
   ],
+  "main": "App.jsx",
   "scripts": {
     "clean": "rm -rf build",
     "start": "webpack-dev-server -d --host 0.0.0.0",

examples/ClubMembers/package.json

@@ -9,6 +9,7 @@
     "validation",
     "react-form-with-constraints"
   ],
+  "main": "App.tsx",
   "scripts": {
     "clean": "rm -rf build",
     "tsc": "tsc",

examples/HTML5ConstraintValidationAPI/package.json

@@ -11,6 +11,7 @@
     "constraints",
     "constraint-validation-api"
   ],
+  "main": "App.tsx",
   "scripts": {
     "clean": "rm -rf build",
     "tsc": "tsc",

examples/MaterialUI/package.json

@@ -11,6 +11,7 @@
     "material design",
     "material-ui"
   ],
+  "main": "App.tsx",
   "scripts": {
     "clean": "rm -rf build",
     "tsc": "tsc",

examples/Password/package.json

@@ -9,6 +9,7 @@
     "validation",
     "react-form-with-constraints"
   ],
+  "main": "App.tsx",
   "scripts": {
     "clean": "rm -rf build",
     "tsc": "tsc",

examples/PasswordWithoutState/package.json

@@ -9,6 +9,7 @@
     "validation",
     "react-form-with-constraints"
   ],
+  "main": "App.tsx",
   "scripts": {
     "clean": "rm -rf build",
     "tsc": "tsc",

examples/PlainOldReact/package.json

@@ -8,6 +8,7 @@
     "form",
     "validation"
   ],
+  "main": "App.tsx",
   "scripts": {
     "clean": "rm -rf build",
     "tsc": "tsc",

examples/ServerSideRendering/package.json

@@ -10,6 +10,7 @@
     "react-form-with-constraints",
     "server-side"
   ],
+  "main": "App.tsx",
   "scripts": {
     "clean": "rm -rf build",
     "tsc": "tsc",

examples/SignUp/package.json

@@ -9,6 +9,7 @@
     "validation",
     "react-form-with-constraints"
   ],
+  "main": "App.tsx",
   "scripts": {
     "clean": "rm -rf build",
     "tsc": "tsc",

examples/WizardForm/package.json

@@ -9,6 +9,7 @@
     "validation",
     "react-form-with-constraints"
   ],
+  "main": "App.tsx",
   "scripts": {
     "clean": "rm -rf build",
     "tsc": "tsc",