Hindawi: add parsing

[drjova]

Add Hindawi publisher files processing DAG. Important information for a task solution:

• The DAG run has to be triggered by one article, coming from fetching DAG (https://github.com/cern-sis/issues-scoap3/issues/86)
• For XML parsing we will use ElementTree
• As an example we can use previous version
• Also we have to consider the following issues while we develop the parsing: https://github.com/cern-sis/issues-scoap3/issues/14

Expected behaviour : Input: XML documents Output - multiple JSONs, one article each.

Acceptance

• Generate a valid record output and give the results to Anne to check that is what we need.

Tests are mandatory

[ErnestaP]

Update: Anne approved the output