Integrate Canary Check

[CMCDragonkai]

Description

This adds a canary root property that is checked for deadbeef string. If it doesn't decrypt, that means the key is wrong, or if the string is not deadbeef, the DB is corrupted.

Issues Fixed

• Fixes #7
• Related to https://github.com/MatrixAI/js-encryptedfs/pull/63#issuecomment-1095005540

Tasks

• [x] 1. Added canaryCheck protected method
• [x] 2. Had to change the _* internal methods to avoid needing to pass db, instead uses this._db and mandates order
• [x] 3. Closes the LevelDB if the start fails

Final checklist

• [x] Domain specific tests
• [x] Full tests
• [x] Updated inline-comment documentation
• [x] Lint fixed
• [x] Squash and rebased
• [x] Sanity check the final build