[jdk25u-dev] RFR: 8343474: [updates] Customize README.md to specifics of update project [v2]

[Goetz Lindenmaier]

> I backport this change from 21!! We should have a similar wording on the github main page.

Goetz Lindenmaier has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'openjdk:master' into goetz_backport_8343474
 - backport 22d5e0d1f8849410abe40165b58f45f5e4293884

-------------

Changes:
  - all: https://git.openjdk.org/jdk25u-dev/pull/26/files
  - new: https://git.openjdk.org/jdk25u-dev/pull/26/files/9fefc65e..5bb9fbf3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk25u-dev&pr=26&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk25u-dev&pr=26&range=00-01

  Stats: 46 lines in 4 files changed: 46 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk25u-dev/pull/26.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u-dev.git pull/26/head:pull/26

PR: https://git.openjdk.org/jdk25u-dev/pull/26