Add tutorial name to tracking links

[agardnerIT]

To efficiently track tutorial usage, we need to modify each background script to push the tutorial name in addition to the pageName.

Do this by adding a new field to the curl -X POST body.

For example:

curl -X POST 'https://b12rzypwjl.execute-api.us-east-1.amazonaws.com/default/keptn_killercoda_tracker' -H 'Content-Type: text/plain' --data-raw '{ "pageName": "intro.md" }'

Becomes:

curl -X POST 'https://b12rzypwjl.execute-api.us-east-1.amazonaws.com/default/keptn_killercoda_tracker' -H 'Content-Type: text/plain' --data-raw '{ "tutorial": "keptnV1", "pageName": "intro.md" }'