docs(github): add pull request template

Author: Kent C. Dodds

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,16 @@
+##########################################################
+#                                                        #
+#                                                        #
+#    This project is unlikely to have any active         #
+#    development due to webpack 2.2.0 having built-in    #
+#    support for validation. Please upgrade webpack      #
+#    and uninstall webpack-validator                     #
+#                                                        #
+#                                                        #
+##########################################################
+
+If you _must_ file a pull request, just know that we'll
+only really consider merging things which are really
+critical for fixing for Webpack 1.x. We're not going to merge
+anything to fix Webpack 2 related issues. Your PR will be
+closed if it's for Webpack 2.