Deprecate Vue 2 support

Author: Kocal

lib/config-generator.js

@@ -133,6 +133,9 @@ class ConfigGenerator {
             switch (vueVersion) {
                 case 2:
                 case '2.7':
+                    logger.deprecation('The support for Vue 2 is deprecated and will be removed in the next major version of Encore.' +
+                        ' Please upgrade to Vue 3, and if necessary remove the "version" setting or set it to 3 when calling ".enableVueLoader()".');
+
                     config.resolve.alias['vue$'] = 'vue/dist/vue.esm.js';
                     break;
                 case 3: