Add example for MySQL Flexible Server Database

quickstart/201-mysql-fs-db/mysql-fs-db.tf

@@ -0,0 +1,7 @@
+resource "azurerm_mysql_flexible_database" "default" {
+  name                = "${var.name_prefix}-db"
+  resource_group_name = azurerm_resource_group.default.name
+  server_name         = azurerm_mysql_flexible_server.default.name
+  charset             = "utf8"
+  collation           = "utf8_unicode_ci"
+}