message: "Tutorial for mongocxx" needs to explain mongocxx::instance
diff: @@ -61,6 +61,10 @@ c++ --std=c++11 <input>.cpp
  ### Make a Connection
  +**IMPORTANT**: Before making any connections, you need to create one and only
  +one instance of [`mongocxx::instance`]({{< api3red classmongocxx_1_1instance >}}).
  +This instance must exist for the entirety of your program.
  +
  To connect to a running MongoDB instance, use the
  [`mongocxx::client`]({{< api3ref classmongocxx_1_1client >}})
  class.
  @@ -74,12 +78,14 @@ The default `mongocxx::uri` constructor will connect to a
  server running on localhost on port `27017`:
  ```c++
  +mongocxx::instance instance{}; // This should be done only once.
  mongocxx::client client{mongocxx::uri{}};
  ```
  This is equivalent to the following:
  ```c++
  +mongocxx::instance instance{}; // This should be done only once.
  mongocxx::uri uri("mongodb://localhost:27017");
  mongocxx::client client(uri);
  ```
  