Add geo_distance proximity filter

Problem/Motivation

Add geo_distance filter implementation : https://www.elastic.co/guide/en/elasticsearch/reference/6.8/query-dsl-ge...

Proposed resolution

Apply patch add-geo_distance.filter.patch
Use https://www.drupal.org/project/search_api_location → for index geofield as latlon type.
Implement Implements hook_search_api_query_alter() and add custom condition :

$proximity = [
"distance" => "12km", // Distance on km
"latlon" => "[lat],[lon]"
];
$query->addCondition('[field_name]', $proximity, 'geo_distance');