Prepare v1.3.0 release - Githubissues

Issue #, if available:

None

Description of changes:

Release 1.3.0 Notes

What's Changed

Ensure that all empty PersistentLists are the same instance. by @popematt in https://github.com/amazon-ion/ion-element-kotlin/pull/91
Fix equals implementation to respect that anyone is allowed to implement IonElement by @popematt in https://github.com/amazon-ion/ion-element-kotlin/pull/88
Use Gradle 8.6, Kotlin build script, and conventional gradle layout by @popematt in https://github.com/amazon-ion/ion-element-kotlin/pull/94
Update README.md by @jobarr-amzn in https://github.com/amazon-ion/ion-element-kotlin/pull/96
Fix broken publishing tasks in build script by @popematt in https://github.com/amazon-ion/ion-element-kotlin/pull/97
Deprecate buildStruct() in favor of idiomatic ionStructOf() overloads by @popematt in https://github.com/amazon-ion/ion-element-kotlin/pull/99
Loader rewrite by @popematt in https://github.com/amazon-ion/ion-element-kotlin/pull/100
Replaces persistent collections with immutable collections by @popematt in https://github.com/amazon-ion/ion-element-kotlin/pull/101
Make loadAllElements fall back to an iterative implementation once a certain depth is reached by @popematt in https://github.com/amazon-ion/ion-element-kotlin/pull/103

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.