Comments not properly parsed

[Enteee]

Describe the bug
One line comments are not properly parsed.

PlantUML

@startuml
' this is a comment
@enduml

yields:

[
  {
    "name": "comment.diag",
    "diagrams": [
      {
        "elements": [
          [
            [],
            "'",
            [
              [
                [
                  null,
                  " "
                ],
                [
                  null,
                  "t"
                ],
                [
                  null,
                  "h"
                ],
                [
                  null,
                  "i"
                ],
                [
                  null,
                  "s"
                ],
                [
                  null,
                  " "
                ],
                [
                  null,
                  "i"
                ],
                [
                  null,
                  "s"
                ],
                [
                  null,
                  " "
                ],
                [
                  null,
                  "a"
                ],
                [
                  null,
                  " "
                ],
                [
                  null,
                  "c"
                ],
                [
                  null,
                  "o"
                ],
                [
                  null,
                  "m"
                ],
                [
                  null,
                  "m"
                ],
                [
                  null,
                  "e"
                ],
                [
                  null,
                  "n"
                ],
                [
                  null,
                  "t"
                ]
              ],
              "\n"
            ]
          ]
        ]
      }
    ]
  }
]

Expected behavior

Should be something like:

[
  {
    "name": "comment.diag",
    "diagrams": [
      {
        "elements": [
          {
             "comment": "this is a comment"
          }
        ]
      }
    ]
  }
]

A clear and concise description of what you expected to happen.