Add support for showing specific sensors to HomeAssistant

[igorkulman]

Description

In the HomeAssistant service I wanted to show the temperature from my sensors. There was no way to do it so I added a generic way to show values from any combination of sensors with icons.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactoring

Checklist:

• I've read & comply with the contributing guidelines
• I have tested my code for new features & regressions on both mobile & desktop devices, using the latest version of major browsers.
• I have made corresponding changes to the documentation (README.md).
• I've checked my modifications for any breaking changes, especially in the config.yml file