New highlight style

[qdequele]

Currently, the engine returns for highlights the fields name, the start of the occurrence and the length.

e.g.

 "matches": [
      {
        "attribute": "xxx",
        "start": 62,
        "length": 7
      }
]

It should be great to have the content of the field with the highlights visible. Set a text before and after the highlight. It should be great for many usages. Like rendering HTML, printing on a terminal, etc. But keep the information starts and length of a match is also interesting in some case.

e.g.

"_highlightResult": {
	"attribute_name": {
		"value": "I am the text of attribute_name and the match is <em>chocolate</em>",
		"matchedWords": [
			"chocolate"
		],
		"matchesPositions": [
			{ "start": 50, "length": 9 }
		],
		"prefixTag": "<em>",
		"postfixTag": "</em>"
	}
},