fix: a couple of fixes and improvements on task --init (#2433)

* Fixed check for an existing Taskfile: look for all possibilities, and
  not only `Taskfile.yml` specifically.
* Added a description (`desc`) to the `default` task. Important to at
  least `task --list` work by default (a core feature).
* Changed top comment to YAML language server comment.

website/src/docs/getting-started.md

@@ -43,6 +43,7 @@ vars:
 
 tasks:
   default:
+    desc: Print a greeting message
     cmds:
       - echo "{{.GREETING}}"
     silent: true
@@ -111,6 +112,7 @@ vars:
 
 tasks:
   default:
+    desc: Print a greeting message
     cmds:
       - echo "{{.GREETING}}"
     silent: true