chore: Add toJSON and fromJSON to AE

[seunafara]

Description

I added the ability to save an autoencoder trained network for later reuse.

Motivation and Context

It solves the problem of not being able to reuse a trained Autoencoder

issue

How Has This Been Tested?

I included a test to the preexisting unit tests.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• [ ✅] New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Author's Checklist:

• [ ✅] My code focuses on the main motivation and avoids scope creep.
• [ ✅] My code passes current tests and adds new tests where possible.
• [ ✅] My code is SOLID and DRY.
• I have updated the documentation as needed.

Reviewer's Checklist:

• I kept my comments to the author positive, specific, and productive.
• I tested the code and didn't find any new problems.
• I think the motivation is good for the project.
• I think the code works to satisfies the motivation.