Publish org.processing.core.pdf to maven Central

[avinxshKD]

Adds Maven Central publishing configuration to the PDF library.

• Added maven-publish plugin
• Added publishing block for local app repository
• Added mavenPublishing block with POM metadata
• Follows same pattern as preprocessor module

Part of #1403

[avinxshKD]

@Stefterv hey started with PDF since it was the easiest.
Let me know if this looks good and I'll work on Net/SVG next. thanks

[Stefterv]

Thanks @avinxshKD I added a few comments ;)

[avinxshKD]

Thanks @avinxshKD I added a few comments ;)

sure was already on it thanks and welcome :)

[avinxshKD]

@Stefterv Updated the coordinates and removed the signing checkk. and
hve skipped the optional migration for this PR to keep it focused on just enabling publishing. Happy to look into a shared plugin in a follow-up refactor for all libraries at once, what do you say?

[avinxshKD]

Ready for another look.

[Stefterv]

The coordinates still need to be fixed, the version should be equal to the processing version, not the version from the library.properties

[avinxshKD]

@Stefterv hve updated the version to use rootProject.version so it matches the Processing version as requested

[Stefterv]

Hi @avinxshKD, it appears to me that you are overly relying on AI for making your changes, please take a look at the "General note about github comments, reviews, and PRs" section of this message.
If not, please copy the coordinates line directly from my pr, only changing the library name

[avinxshKD]

@Stefterv so sorry. Been swamped with exams lately,will be more careful reviewing before pushing.
Made the changes u asked thanks

[Stefterv]

No worries @avinxshKD thank you for the changes they look great 💙