Add feedback link to main help menu (#49)

Adds the feedback board link only to the root help menu.

This also re-enables all of the descriptions for each command at the top
of the command or sub-command help menu.

Author: Chaseshak

src/ActionsImporter/Program.cs

@@ -15,7 +15,11 @@
     new ConfigurationService()
 );
 
-var command = new RootCommand("GitHub Actions Importer is a tool to help plan and automate your migration to Actions.")
+string welcomeMessage = @"GitHub Actions Importer helps you plan, test, and automate your migration to GitHub Actions.
+
+Please share your feedback @ https://gh.io/ghaimporterfeedback";
+
+var command = new RootCommand(welcomeMessage)
 {
     new Update().Command(app),
     new Version().Command(app),
@@ -31,8 +35,8 @@
     {
         ctx.HelpBuilder.CustomizeLayout(_ =>
             HelpBuilder.Default
-                .GetLayout()
-                .Skip(2)
+              .GetLayout()
+              .Where((_, i) => i != 1) // Remove the usage section (second item in the help layout)
             );
     })
     .UseEnvironmentVariableDirective()