Add version supporting serialization 1.5.1 but keeping kotlin as 1.8.10

[duarteffc]

Hi @pdvrieze. Thanks for this util.

We have a need in our project to continue supporting 1.8.10 but running serialisation version 1.5.1. It should be v0.85.1, I believe.
We can open a branch with the changes as long as we have permissions.

Thanks!

[pdvrieze]

Hi, I've had a look at it. I have pushed a small change to dev that makes things work with 1.8.21 (not relying on the 1.9 implementation of kotlin.assert) and sets the target apiLevel to 1.8.
At the same time the module compiles and checks against serialisation 1.5.1 (when disabling the wasm targets that don't exist with the older versions).

In combination it should be possible to use the library with an overridden version of kotlinx.serialization. As such you should be able to just do some gradle adjustments to dependencies. (Have a look at: https://docs.gradle.org/current/userguide/dependency_downgrade_and_exclude.html).

If that doesn't work, let me know