Clarification of what to expect from major and minor releases after 9.5

[Bastien]

Hi all,

I've updated https://orgmode.org/worg/org-maintenance.html to clarify
a few points:

- we don't have a release schedule;

- after Org 9.5, x.y versions like 9.6, 9.7, etc. will be *minor
  versions*, not major versions.  So the next major after 9.5 is 10.

- we don't follow semantic versioning: that is, we use the familiar
  numbering sheme (x.y.z) but the distinction between major (x) and
  minor (y) is not about incompatible vs compatible changes.  

  Instead, we use what I'd call "Hear ye!" versioning: major Org
  versions request every users to read the release notes, and minor
  Org versions request Org contributors and power users to read the
  release notes.  We have no release notes for bugfix-only release.

Let me know if something is not clear!

All best,

-- 
 Bastien