[openssl-project] Update release strategy to document new versioning scheme

[Matthias St. Pierre]

Hi,

I just happened to notice that the Release Strategy [1] on our homepage is
outdated w.r.t. the versioning scheme: It still calls the 1.x.y versioning scheme
the 'improved' one, and does not mention the new 3.0.0+ scheme at all.

> As of release 1.0.0 the OpenSSL  versioning scheme was improved
 > to better meet developers' and vendors' expectations. Letter
 > releases, such as 1.0.2a, exclusively contain bug and security
 > fixes and no new features. Minor releases that change the last
 > digit, e.g. 1.1.0 vs. 1.1.1, can and are likely to contain new
 > features, but in a way that does not break binary
 > compatibility. ...

In fact, the only official mentions of the new versioning scheme are the blog post [2]
from November 28 and (indirectly) the License page [3] because it has been
updated for the Apache relicensing.

So maybe `releasestrat.html` needs an update? You could also add a separate
`versioning.html` for versioning details, if you don't want to overload `releasestrats.html`.
The contents of `versioning.html` could be taken partially from [1] and [3].


Matthias

[1] https://www.openssl.org/policies/releasestrat.html
[2] https://www.openssl.org/blog/blog/2018/11/28/version/
[3] https://www.openssl.org/source/license.html