feat(docs): [SCv2] Automatically create and upload a custom HF model to seldon-models in GCS on every new MLServer version

[vtaskow]

What this PR does / why we need it:
The next version of MLServer will be allowing users to create custom HuggingFace models. Users will be able to specify a location in which model artefacts will be located and later used. This will allow users to customize certain model parameters, such as tokenizers, feature extractors, image processors, etc and then build a HuggingFace model and use it, not limiting themselves to existing models on the official hub.

Automating the creation and the upload of a simple custom HuggingFace model to our collection of models in our GCS bucket - seldon-models, will pave the way to use said model in upcoming demos, showcasing how users can actually load a custom model and use it in SCv2 or in our paid products.

By having this automation, we ensure that on every new MLServer version release, the custom HF model is added to our collection of models in the bucket and demo pages are kept up-to-date.

Testing

• The resulted model was generated correctly by running make text-generation-huggingface
• The generated model was uploaded correctly to a public GCS bucket(mine in this case) by running make upload-text-generation-huggingface
• Used the Seldon CLI to load a Model K8s resource, pointing to a GCS location with a custom HF model and correctly predicted

Seldon Deploy Testing

• Passed said model GCS location in Seldon Deploy Wizard and successfully created and predicted for a Deployment and for a Pipeline

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

[adriangonz]

👍