Add recommendations on Publishing libraries to Maven Central

publishing-libraries-to-maven-central.md

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+# Publishing libraries to Maven Central
+
+[Maven Central](https://central.sonatype.com/), administered by [Sonatype](https://www.sonatype.com/),
+is the de-facto artifact repository for JVM-based languages like Scala & Kotlin - for Typescript/JavaScript,
+the equivalent would be the [npm Registry](npm-packages.md).
+
+At the Guardian we publish many libraries to Maven Central, and are standardising on reusable automated
+GitHub Action release workflows with these aims:
+
+* **achieve zero-onboarding for new developers**: Any developer who has `write` access to a repo should be able
+  to publish a release of the library, at the click of a button.
+* **securely handle release credentials** - only allow access to release credentials for parts of the release process
+  that [_need_](https://github.com/guardian/gha-scala-library-release-workflow/blob/main/docs/security-design.md) them.
+* **automated version compatibility checking** - to avoid [binary-incompatibility causing runtime errors](https://github.com/guardian/facia-scala-client/issues/301).
+* **reduce per-repo config** - adding library-publishing to a repo should add _minimal_ boilerplate.
+
+## Admin access
+
+As our automated GitHub Action workflows provide all the access that most users need, we have
+[very few user accounts](https://docs.google.com/spreadsheets/d/1B_XYsuxNwBuvJ9o72iqgerSeql97bEJw5pT9P5i9A5E/edit?usp=sharing)
+with direct admin access to Maven Central/Sonatype. If necessary, see the [docs](https://docs.google.com/document/d/1zA8CHa1a8faemorWokUlbkdexYzpilalqcPFwkRu92M/edit?usp=sharing)
+on credential rotation & account recovery.
+
+# Scala libraries
+
+Scala is our most common language for JVM-language artifacts. Any Guardian repo publishing a library
+should use [`gha-scala-library-release-workflow`](https://github.com/guardian/gha-scala-library-release-workflow),
+which provides many lovely [benefits & features](https://github.com/guardian/gha-scala-library-release-workflow/blob/main/docs/benefits.md).
+
+See [how to configure a repo to use the workflow](https://github.com/guardian/gha-scala-library-release-workflow/blob/main/docs/configuration.md).
+
+# Kotlin libraries
+
+We're working on adopting a similar approach for our Android/Kotlin libraries, see eg:
+
+* https://github.com/guardian/source-apps/pull/10