Add endStyle attribute to DocCommentStyle

[EliteMasterEric]

In order to match the comment style used as standard in languages like JavaScript, asymmetrical start and end styles must be used, like so:

/**
 * Test
 */

a new configuration option is needed for the DocCommentStyle rule: https://haxecheckstyle.github.io/docs/haxe-checkstyle/doccommentstyle.html

{
  "type": "DocCommentStyle",
  "props": {
    "startStyle": "twostars",
    "lineStyle": "oneStar",
    "endStyle": "oneStar"
  }
}

For compatibility, this option should default to the current value of startStyle.