add toml example, use yaml in help doc

Signed-off-by: Andrey Nering <andrey.nering@gmail.com>

example/Taskfile.json

@@ -8,4 +8,4 @@
       "output.txt"
     ]
   }
-}
+}

example/Taskfile.toml

@@ -0,0 +1,3 @@
+[hello]
+cmds = ["echo \"I am going to write a file named 'output.txt' now.\"", "echo \"hello\" > output.txt"]
+generates = ["output.txt"]