content: IonicSafeString does not have a Vue example

### URL

https://ionicframework.com/docs/techniques/security#usage

### Issue Description

For `IonicSafeString` to work correctly with Vue, it has to be imported from `@ionic/vue`, not `@ionic/core`. In the absence of an example we are not sure where to import from, specially since it is exported from both packages.

Please add a Vue example.

Open the linked security documentation page and inspect its Usage section. Add an example showing IonicSafeString imported from @ionic/vue for Vue, clarifying the correct package to use. Done means the page includes a working Vue example alongside the existing usage guidance.

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