Allow a Storage implementation to be passed into the LocalStorage adapter

[cusspvz]

The current implementation of the LocalStorage adapter relied directly on the browsers window.localStorage. These changes maintain the current behavior and allow devs to initialize the LocalStorage with a different Storage interface. I've defined the Storage interface to allow synchronous or asynchronous methods.

This change also allows LokiDB to persist information on platforms that don't offer indexedDB or FS. This is the case for React Native, or other implementations that don't support IndexedDB, by allowing devs to provide a storage interface, React Native's Async Storage can now be fed to LokiDB as a persistent storage mean.

Also took the chance that I had to edit the tests to ensure other implementations could fit into those interfaces, so I've introduced 2 mocked-storages, async and sync, to ensure the intended behavior works as expected. As the tests were not using the async/await feature, ended up rewriting those.

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/LokiJS-Forge/LokiDB/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information