hg: openjfx/12-dev/rt: 8228424: create release notes for 12.0.2

[johan at lodgon.com]

Changeset: 35459041f231
Author:    jvos
Date:      2019-07-19 15:00 +0200
URL:       https://hg.openjdk.java.net/openjfx/12-dev/rt/rev/35459041f231

8228424: create release notes for 12.0.2
Reviewed-by: kcr

+ doc-files/release-notes-12.0.2.md