[FEATURE] Support author email in changelog

[tqwewe]

Is your feature request related to a problem? Please describe.
There's no way currently to specify an authors email address in the changelog settings in cog.toml.

Describe the solution you'd like
Add support for email in cog.toml under changelog.authors:

[changelog]
authors = [
    { signature = "Ari Seyhun", username = "Acidic9", email = "ariseyhun@live.com.au" },
]

It might also be nice to support a string directly, as seen in Cargo toml files and many other places:

authors = [
    "Ari Seyhun <ariseyhun@live.com.au>"
]