Add url to pushover notification

[aizatto]

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Description

The Pushover API allows an URL to be included in the HTTP Request. This can help for better user experience to quickly open the Uptime Kuma dashboard.

https://pushover.net/api

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 generates no new warnings
• My code needed automated testing. I have added them (this is optional task)

Screenshots (if any)

Before:

After:

Notice the url is included.

[CommanderStorm]

Thanks for the change to the notification provider! 🎉

Note

This PR is part of the v2.0 merge window => see #4500 for the bugs that need to be addressed before we can ship this release ^^

_{All changes in this PR are small and uncontroversial ⇒ merging with junior maintainer approval}

[aizatto]

New screenshot: