Nostr dm notifications

[zappityzap]

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Description

Resubmitting #3051
Adds nostr direct messages as a notification provider.

Changes:

• Replaced websocket-polyfill with ws, to support arm v7
• Updated nostr-tools to 1.13.1
• Updated deprecated function signEvent with getSignature

Type of change

Please delete any options that are not relevant.

• New feature (non-breaking change which adds functionality)

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and tested it
• I have commented my code, particularly in hard-to-understand areas
  (including JSDoc for methods)
• My changes generate no new warnings
• My code needed automated testing. I have added them (this is optional task)

Screenshots (if any)

Please see previous PR for screenshots