Consider suggesting Visual Studio Code for working with GitHub in Getting Started guide

[StevenMaude]

I'm reviewing the Getting Started guide at the moment. (This isn't in scope for me right now, but could be a good idea, so noting it.)

Advantages here:

• the coding interface essentially looks the same whether running in Codespaces or local Visual Studio Code
• the use of GitHub Desktop could be dropped, because Visual Studio Code can handle pushing commits

[StevenMaude]

Looking more, we already suggest it as an editor.

We could:

• suggest it for committing and pushing to GitHub too
• move the installation step to earlier where all the other software is installed