Feature: Use localForage instead of localStorage

[sy-records]

Feature request

Use localForage instead of localStorage.

Problem or desire

Solve the problem that too many search indexes cannot be stored in localStorage.

Proposal

https://github.com/localForage/localForage

Implementation

Because localForage uses async storage, it has an async API. It's otherwise exactly the same as the localStorage API.

Should just need to replace localStorage in src/plugins/search/search.js