Elixir Security - (De-)Serialization

[houllette]

We should continue rounding out what is included from the EEF's research into the module for Elixir Security and add the "(De-)Serialization" lesson.

Relevant Resource:

• https://erlef.github.io/security-wg/secure_coding_and_deployment_hardening/serialisation

[stilwellc]

tracked in the other Elixir PR, didnt want to over complicate things