Gather and return location of string matches

[sckott]

e.g. gnparser has for the name Pseudocercospora

{
  "name_string_id": "9c1167ca-79e7-53de-b4c3-fcdb68410527",
  "parsed": true,
  "quality": 1,
  "parser_version": "test_version",
  "verbatim": "Pseudocercospora",
  "normalized": "Pseudocercospora",
  "canonical_name": {
    "value": "Pseudocercospora",
    "value_ranked": "Pseudocercospora"
  },
  "hybrid": false,
  "surrogate": false,
  "virus": false,
  "bacteria": false,
  "details": [
    {
      "uninomial": {
        "value": "Pseudocercospora"
      }
    }
  ],
  "positions": [
    [
      "uninomial",
      0,
      16
    ]
  ]
}

this doc section shows some example of grabbing position for error reporting https://github.com/taocpp/PEGTL/blob/master/doc/Inputs-and-Parsing.md#error-reporting which can perhaps be used