Split void into multiple separate rules

Currently the rule void does multiple validations:

• void-elements must not have content (e.g. <input>, <hr>, etc)
• void-elements must be closed using the configured style: omit <input> or self-closing <input/>.
• non-void-elements must always have a close tag.

This is fine as long as the defaults are ok but is not very flexible to configure.

Suggesting to split this into three separate rules:

• void-element ensures that an element with "void": true cannot have any content. Test this by ensuring that there are no children at al (no elements, text nodes, etc).
  Default: error
• void-style ensures the correct style when "void": true
  Default: error, style: omit
• no-self-closing ensures that elements "void": false isn't self-closed.
  Default: error

Use cases

• Allow user to configure that empty tags (no content) may be self-closing tag but close tag if content is present, e.g both <my-foo/> and <my-foo>bar</my-foo> should be valid under this configuration:
  "no-self-closing": false

Acceptance tests

	Default config	void-element	void-style omit	void-style self-closing	no-self-closing
<input>				error
<input/>	error		error
<input></input>	error	error
<input>foo</input>	error	error
<div/>	error				error