Prep for 0.6 release of napari

[willingc]

Since folks are likely going to use this with the changes around the npe2 adaptor and 0.7 deprecation, let's do a little polishing here:

• update README to reflect current state of template Update README for recent template updates #21
  • add copier badge
  • add npe2 badge
  • add note that copier can be run over an existing project https://copier.readthedocs.io/en/stable/faq/#can-copier-be-applied-over-a-preexisting-project
• audit pyproject.toml.jinja Update pyproject.toml.jinja to drop python 3.8 and 3.9 #22
• change foobar prompts to something more domain friendly instead of coder friendly
• if possible, show how to take an old plugin to npe2 with the template's support #44

[TimMonko]

From Peter in #38

Really nice!
One quick followup PR to this would be to in Step 1 also use conda to setup the virtual env. It's what we use throughout the napari docs (at least at present), so it's good to have it here. I've never used venv before but am terrified what python version that would use on my system, like python 2 or something?!
I'm not a very advanced user though, so I might be missing something, so please feel free to disregard!

[TimMonko]

Almost done with this. I'm thinking that taking an old plugin to npe2 with the template is a bit of a bigger lift than we have room for at the moment.

But, it's definitely still on my radar. At the very least I want to add support for .copier-answers and making updates to templates as things change. Say we changed the github workflows, would be nice to use the templates to update them.

[willingc]

Let's call this done and I will open an issue to keep the last one on the radar.