Require retired/current browser releases to have release_date

[caugner]

What would you like to see added to BCD?

The browers schema does not require the release_date field, mainly to account for upcoming not yet released releases, but all retired and current should have a release_date, and this is not enforced.

How impactful do you think this enhancement will be?

This enhancement ensures that all released browser releases can be sorted by release date, and it avoids problems for users that depend on released browser releases to have a release date.

Do you have anything more you want to share?

No response