[web-db] start persisting SQLite content

Summary:
Saving database file in indexed db

Depends on D7185

Test Plan:

1. Check in devtools if indexedDB key exists
2. Reopen app and save something into db - database should be read from the indexed db, not freshly created

Reviewers: michal, tomek

Reviewed By: tomek

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D7186