[create-gatsby] Enable use of current directory when creating a new project

[mithenks]

Description

When starting a new project using Gatsby CLI, if I run gatsby new . I can create a new project in the current directory.
It will be very useful if I can specify to use current directory also in the interactive steps when I run only gatsby new.

Steps to reproduce

Run gatsby new in the command line.
When you are asked "What would you like to name the folder where your site will be created?", you cannot specify .(current directory) as value.

Expected result

I can tell gatsby CLI to use current directory as project root.

Actual result

The new gatsby project is created in the current directory.

Environment

  System:
    OS: Linux 4.19 Debian GNU/Linux 10 (buster) 10 (buster)
    CPU: (1) x64 Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
    Shell: 5.0.3 - /bin/bash
  Binaries:
    Node: 14.17.0 - /usr/local/bin/node
    Yarn: 1.22.5 - /usr/local/bin/yarn
    npm: 6.14.13 - /usr/local/bin/npm
  npmGlobalPackages:
    gatsby-cli: 3.7.1