Add highlight implementation for redisearch adapter

[alexander-schranz]

Add support for:

$searchBuilder
    ->addIndex('blog')
    ->addFilter(new Condition\SearchCondition('Test'))
    ->highlight(
        fields: ['title', 'description'],
        preTag: '<mark>',
        postTag: '</mark>',
    );

TODO

• Find a way for following issue: [Help] Highlighting unexpected error No such property title RediSearch/RediSearch#4420