MM-19477: model extra manifest data (#12823)

Model `HomepageURL` and `SupportURL` for use in listing plugins in the marketplace.

model/manifest.go

@@ -130,6 +130,12 @@ type Manifest struct {
 	// A description of what your plugin is and does.
 	Description string `json:"description,omitempty" yaml:"description,omitempty"`
 
+	// HomepageURL is an optional link to learn more about the plugin.
+	HomepageURL string `json:"homepage_url,omitempty" yaml:"homepage_url,omitempty"`
+
+	// SupportURL is an optional URL where plugin issues can be reported.
+	SupportURL string `json:"support_url,omitempty" yaml:"support_url,omitempty"`
+
 	// A relative file path in the bundle that points to the plugins svg icon for use with the Plugin Marketplace.
 	// This should be relative to the root of your bundle and the location of the manifest file. Bitmap image formats are not supported.
 	IconPath string `json:"icon_path,omitempty" yaml:"icon_path,omitempty"`