git: openjdk/jfx23u: master: 8304008: Update README.md and CONTRIBUTING.md for jfx update repos

[Kevin Rushforth]

Changeset: 20ead5a1
Branch: master
Author:    Kevin Rushforth <kcr at openjdk.org>
Date:      2024-07-18 12:18:59 +0000
URL:       https://git.openjdk.org/jfx23u/commit/20ead5a13e2666e33b6871bd3b8ff97f020c8ea8

8304008: Update README.md and CONTRIBUTING.md for jfx update repos

Reviewed-by: jvos
Backport-of: 632792d4e7a6399c156df99b1cf69faba476a8c6

! CONTRIBUTING.md
! README.md