feat: caching containers

[kuraisle]

✨ Feature

PR Description

I've added caching behaviour to the container build workflow.
The way caching works with docker/build-push-action is that the action has cache-from and cache-to fields under with.

The way I've chosen to add this to the workflow is to add string inputs for cache-from and cache-to. There are lots of options to choose; I have used what works with the omop-r-tools build, which is also in docker's example.

I had worried that passing arguments as a string, or passing an empty string, would cause strange behaviour. I tested this in the omop-r-tools repo:

• Passing the arguments as a string works
• Passing an empty string means no caching note: I cancelled this run once I confirmed it wasn't caching layers

Related Issues or other material

Related #43
Closes #43

✅ Added/updated tests?

• This PR contains relevant tests / Or doesn't need to per the below explanation

[github-actions]

🎉 This PR is included in version 1.6.0 🎉

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