Explore Transifex GitHub integration

[jnm]

@tinok reports:

The integration is only enabled for the organization, it's not yet enabled for kpi (which is done on the project settings page).
I won't enable it. The documentation for how to use it to automatically
pull new strings and to make PRs when new translations are available
(and at what % they need to be in terms of completion) is found here.

Perhaps we could eliminate this repository if the integration works.

[jnm]

If we do keep this repository, we should have pin the revision of this submodule when doing KPI releases, since the translatable strings in KPI are different from one release to the next.