add drop into chunk values tags

[oalam]

analyse SAX string and check if there's a 2 or 3 letter drop and add a tag accordingly with correct timestamp

[MiniPlayer]

Related to #5 ,
The tags should be added in a separate Collection than chunks.
We called for exemple this collection "annotations".
Each particular event would be indexed in this collection in the following format :

  {
    "time": 1581075145188,
    "timeEnd": 1581075145188,
    "text": "drop of 3 detected",
    "tags": [
      "metric_1", "drop"
    ]
  }