Proposed schedule for JavaFX 15

[Kevin Rushforth]

Here is the proposed schedule for JavaFX 15.

RDP1: Jul 2, 2020 (aka “feature freeze”)
RDP2: Jul 30, 2020
Freeze: Aug 20, 2020
GA: September 8, 2020

We plan to fork a jfx15 stabilization branch at RDP1. The GA date is 
expected to be one week ahead of JDK 15, matching what we did for 14.

As a slight change from previous releases, the start of RDP1, the start 
of RDP2, and the code freeze will be 16:00 UTC on the respective dates.

Please let Johan or me know if you have any questions.

-- Kevin