[ENH] Default environment.yml spec needs improvement

[kcpevey]

The Create New Environment page current looks like this

But I'd suggest that this default environment.yml is not helpful because when people typically write conda environment.yml files they usually look like this:

channels:
  - conda-forge
dependencies:
  - python=3.10
  - boto3

What I need from the default environment spec is help remembering what the yaml template looks like (i.e. colons, dashes, spacing, etc).

I propose that the default environment spec for new environments look like this:

channels:
  - 
dependencies:
  -