Optional feature to cache SSM configuration

[garrett-mayer]

@gunnargrosch

What do you think about an optional feature to cache the SSM config value?

We've ran into some SSM throttling issues while running load tests on our lambdas.

• https://docs.aws.amazon.com/general/latest/gr/ssm.html | GetParameter is 40 requests per second by default

Ideally, we'd like to cache the value for a configurable amount of time.

Thoughts? I don't mind providing a PR to this project or simply forking the project either.

[gunnargrosch]

I like that! I think I have some notes around that already. Let me find those and post back here.

[garrett-mayer]

@gunnargrosch I've created a PR for this feature. #39

Please take a look & let me know what you think - I'm happy to make any changes.

I wasn't quite sure how you wanted to document this feature - so I took a shot at updating the docs as well.