Fix deprecated email key in the default _config.yml file

It's now under an `author` key:
https://github.com/jekyll/minima?tab=readme-ov-file#author-metadata

Also added a sample `author.name` key.

lib/site_template/_config.yml

@@ -14,12 +14,14 @@
 #
 # Site settings
 # These are used to personalize your new site. If you look in the HTML files,
-# you will see them accessed via {{ site.title }}, {{ site.email }}, and so on.
+# you will see them accessed via {{ site.title }}, {{ site.author.email }}, and so on.
 # You can create any custom variable you would like, and they will be accessible
 # in the templates via {{ site.myvariable }}.
 
 title: Your awesome title
-email: your-email@example.com
+author:
+  name: Your Name
+  email: your-email@example.com
 description: >- # this means to ignore newlines until "baseurl:"
   Write an awesome description for your new site here. You can edit this
   line in _config.yml. It will appear in your document head meta (for