Update README and CONTRIBUTING guidelines for this repo as appropriate for update releases (basically a copy from jfx17u with 17 changed to 20).
------------- Commit messages: - 8304008: Update README.md and CONTRIBUTING.md for jfx update repos Changes: https://git.openjdk.org/jfx20u/pull/2/files Webrev: https://webrevs.openjdk.org/?repo=jfx20u&pr=2&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8304008 Stats: 267 lines in 2 files changed: 1 ins; 254 del; 12 mod Patch: https://git.openjdk.org/jfx20u/pull/2.diff Fetch: git fetch https://git.openjdk.org/jfx20u pull/2/head:pull/2 PR: https://git.openjdk.org/jfx20u/pull/2
