Publish 0.8.0

• Publish now uses (and requires) Swift 5.4.
• Full support has been added for Plot's new component-based API, with dedicated Component implementations for markdown rendering (Markdown), video playback (VideoPlayer), and the ability to use Plot's AudioPlayer component with Publish's Audio models.
• Since Publish now contains a type called Markdown, if you want to refer to Ink's type with the same name, you have to use Ink.Markdown. That's the only potentially breaking change within this release, and should hopefully not have a big impact on any Publish-based code base.
• The Content.Body type can now also be used directly as a Plot component.
• You can now specify what Git branch to deploy to when using the .git and .gitHub deployment methods (by @Kilo-Loco).
• If you generate a website called "Website" using the Publish CLI, the generator will now prefix the Website protocol with Publish as to not cause conflicts with the website definition itself (by @sviatoslav).
• When generating site map files, the excludedPaths argument is now interpreted as a prefix, rather than using absolute string matching, which enables you to exclude entire sections/folders at once (by @bensyverson).