Offline mode

[vdkdamian]

New Pull Request Checklist

• [x] I am not disclosing a vulnerability.
• [x] I am creating this PR in reference to an issue.

Issue Description

This adds the possibility to use ParseSwift with offline mode. Objects will be stored on device if needed and can be fetched when internet connection is back.

Approach

I will add playground examples on how to use it.

TODOs before merging

• [ ] Test
• [ ] Add tests
• [ ] Add entry to changelog
• [ ] Add changes to documentation (guides, repository pages, in-code descriptions)
• [ ] Add playground examples

[parse-github-assistant[bot]]

Thanks for opening this pull request!

• ❌ Please link an issue that describes the reason for this pull request, otherwise your pull request will be closed. Make sure to write it as Closes: #123 in the PR description, so I can recognize it.