TTML2 test suite and implementation report

Hi all,

As discussed this morning, in order to meet the earliest possible deadline
for publication of the PR, we need to have the test suite and
implementation report ready by September 27. Once the test suite is ready,
we should leave time for people to actually check their implementations
against it. We have 255 features in TTML2. We agreed to test only the
additional ones compared to TTML1. This means 255-114 = 141 features. Given
the volume, I think we nee to give people a week to check all those tests
(possibly produce images to check interop) and update the report. So the
test suite should be ready before Sept 20. Do you agree?

How do we organize the development of the test suite:
- Who can provide tests?
- How do we avoid duplicating the work?
- I see that https://github.com/w3c/ttml2-tests contains some tests
already, in a validation folder. What does it mean? Do we foresee
"validation" tests and "rendering" tests or are they going to be the same?

@Glenn, you indicated that you have many tests already:
 - Can you provide them for August 13?
 - Out of the new 141 features, how many features are tested by your tests?
How many feature are missing? Can we distribute the work to create the
missing one among other members?

Cyril