Pushover add UP/DOWN status sounds

[sebastian-mora]

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Description

Fixes #1953

Adds the ability to select Up and Down sounds for pushover notifications. As before if no/or of the options are selected then the device default sound is used.

To keep backwards compatibility I added notification.pushoversounds_up which is used if the heartbeat event is UP.

One note is the UP/DOWN text on the fields is not translated.

Type of change

Please delete any options that are not relevant.

• User interface (UI)
• 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)

[CommanderStorm]

Seems reasonable.
I have left two review comments below and have added this to the v2.1 slot

[sebastian-mora]

Thank you for the review!