feat : adds functionality to import and export IPNS keys in the IPFS WebUI

[shobit000]

Summary

This PR adds functionality to import and export IPNS keys in the IPFS WebUI.

Changes

• Added functions for importing and exporting IPNS keys in src/bundles/ipns.js.
• Updated IpnsManager component to include UI elements for importing and exporting IPNS keys in src/components/ipns-manager/IpnsManager.js.
• Added translation strings for "Import Key" and "Export Key" in public/locales/en/settings.json.

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[SgtPooki]

thanks for throwing this together quickly.