Adopting SponsorLink in v1.3.0+

[kzu]

In order to improve the long-term sustainability of this (and other) projects, we'll be adopting SponsorLink v2.

Please get familiar with it, read the privacy statement and raise any doubts related to it in the SponsorLink repo itself.

All of SponsorLink is OSS too.

What this means for you:

1. If you're not a sponsor (or you haven't synchronized your sponsorship), you will get a IDE-only warning reminding you that you can sponsor the project.
2. CLI or CI builds will never check for sponsorship.
3. You don't need to sponsor if you're an OSS author/contributor yourself (unless you want to, of course).

[kzu]

Superseded by #153