JavadocParagraph: Allow disable empty line check

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I am using [PegdownDoclet](https://github.com/Abnaxos/markdown-doclet) in my Java project, thus I could safely document JavaDoc in Markdown format, in which case the `

` tag is not required.

However I found checkstyle always report:

```
Empty line should be followed by

tag on the next line.
```

And I can't find any configuration to disable it.

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This request is to have checkstyle provides a configuration to disable the empty line check

Start with the JavadocParagraph check and its existing configuration and diagnostic for empty lines. Add a configuration option that disables this check, then verify that JavaDoc using Markdown-style paragraphs no longer reports the empty-line error while the default behavior remains unchanged.

Written by the indexing model from the issue text.