Document extension functions in store.kt

[blakelee]

Closes #668

Description

This PR adds documentation to store.kt so that it's easier to grok all the different types that there are. Along with calling out needing to handle exceptions otherwise there could be potential crashes that are hard to find within your logging.

Type of Change

• This change is a documentation update

Checklist:

Before submitting your PR, please review and check all of the following:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my change is effective
• New and existing unit tests pass locally with my changes

[matt-ramotar]

Thanks!

[blakelee]

Fixed the sign off