Migrate documentation from Wiki to GitHub

[0xShubhamSolanki]

Description

This PR migrates the plugin documentation from the Jenkins Wiki export to the GitHub README.

The existing README was very minimal and had not been updated in many years.
I have restructured the documentation in Markdown format and moved the relevant content from the Wiki export, including:

• Description
• Installation steps
• Configuration details
• Usage section
• Known issues
• Changelog

I also added a simple Pipeline usage example to make the documentation clearer for users.

This follows the documentation migration effort described in JENKINS-59467.

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Testing done

This change only updates documentation.

I verified that the Markdown renders correctly in the GitHub preview.
No source code or runtime behavior was modified.

[MarkEWaite]

Thanks very much!

I've requested several changes.

Please also update pom.xml and replace https://wiki.jenkins-ci.org/display/JENKINS/JDK+Parameter+Plugin with the value described in the tutorial and the more detailed steps.

[MarkEWaite]

Thanks!

[0xShubhamSolanki]

Thank you for the review and guidance on this PR. I really appreciate the feedback and the opportunity to contribute.
I’m planning to stay actively involved with Jenkins this year and would be glad to help further. If there are specific areas where help is needed, I’d appreciate any suggestions.