Add pymakr as a recommended VS Code Extension

When creating a new project with ```micropy init```, and the user selects "Pymakr configuration", add PyMakr as a recommended Extension in the VS Code extensions.json file.

## Background
I am very new to micropy (and micropython in general), so my apologies if I am missing something really obvious as to why this is a dumb request.

I am writing a short guide for a teenage nephew, so he can quickly get started in MicroPython on the ESP32, and I want minimum steps possible to get him up and running. MicroPy-cli is looking like a superb way to get started quickly. Hopefully my suggestion would mean one less step :)