Add scheduler to clean up expired sessions

[interpretor]

Closes #25.

Checklist:

• [x] issue number linked above after pound (#)
  • replace "Closes " with "Contributes to" or other if this PR does not close the issue
• [x] manually checked my feature / checking not applicable
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As unstorage doesn't implement a touch/expire functionality, we need to check periodically for expired sessions. A simple cron job iterating over the keys with our prefix in the storage will check if the session is expired, and then delete it from the store.

I hardcoded a fixed cleanup interval, we could discuss if this should be configurable or set to another value other than every minute.

[AnthonyRuelle]

Hi !

Why is this PR not merged yet? I also noticed this problem ..

[AnthonyRuelle]

Up, please .. @BracketJohn ?