[jdk8u-dev] RFR: 8251551: Use .md filename extension for README

[Paul Hohensee]

On Mon, 27 Nov 2023 17:33:22 GMT, Zdenek Zambersky <zzambers at openjdk.org> wrote:

> This backport adds `.md` extension to README. It also changes formulations a bit and adds some hyperlinks. Backport is not clean because there were small intermediate changes to README by (changesets not applicable to JDK8):
> - [JDK-8187444](https://bugs.openjdk.org/browse/JDK-8187444)
> - [JDK-8205956](https://bugs.openjdk.org/browse/JDK-8205956)
> 
> (Git however considers this rewrite anyway.)

Looks like a clean backport from 11u. GHA test failure appears unrelated (this PR doesn't affect GC).

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Marked as reviewed by phh (Reviewer).

PR Review: https://git.openjdk.org/jdk8u-dev/pull/394#pullrequestreview-1751626744