Add publishing configuration to plugins

[gpunto]

No description provided.

[Copilot]

Pull Request Overview

This PR adds Maven publishing configuration support to the Stream build conventions plugin, enabling automatic publishing for library and platform modules.

• Introduces new publishing configuration with customizable artifact IDs and descriptions
• Adds a new Java platform convention plugin (io.getstream.java.platform)
• Refactors the findOrRegister utility function to a shared location for reuse

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
plugin/src/main/kotlin/io/getstream/android/publishing/PublishingOptions.kt	New configuration class defining publishing options with description and artifact ID overrides
plugin/src/main/kotlin/io/getstream/android/publishing/PublishingConfiguration.kt	Core publishing logic integrating vanniktech maven-publish plugin with Dokka for documentation
plugin/src/main/kotlin/io/getstream/android/GradleUtils.kt	Extracted findOrRegister utility function for shared task registration logic
plugin/src/main/kotlin/io/getstream/android/spotless/SpotlessConfiguration.kt	Refactored to import findOrRegister from shared utilities instead of local definition
plugin/src/main/kotlin/io/getstream/android/StreamConventionPlugins.kt	Added JavaPlatformConventionPlugin and integrated publishing into library plugins
plugin/src/main/kotlin/io/getstream/android/StreamConventionExtensions.kt	Extended project configuration with publishing options
plugin/build.gradle.kts	Added maven-publish and dokka plugin dependencies, registered new Java platform plugin
gradle/libs.versions.toml	Added maven-publish and dokka library references, removed unused gradle-plugin-publish
README.md	Updated documentation with publishing configuration examples and versioning instructions

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[gpunto]

We don't necessarily want to checkout from develop when publishing a snapshot.

[gpunto]

Downgrading for the time being, because I don't want to bundle all the changes for the migration to the publishing configuration with the changes needed for migrating to Dokka v2 in products. I'll do the upgrade later.