New template sensor attributes

[gadgetchnnel]

Description:

Similar to PR #22664, which did this for the template binary sensor, this adds an option to add custom attributes to the sensor via a new attribute_templates config option.

Related issue (if applicable): fixes #

Pull request with documentation for home-assistant.io (if applicable): home-assistant/home-assistant.io#10204

Example entry for configuration.yaml (if applicable):

sensor:
  - platform: template
    sensors:
      test_sensor:
        value_template: >-
          {{ states.device_tracker.my_phone.state }}
        attribute_templates:
          latitude: >-
            {{ states.device_tracker.my_phone.attributes['latitude'] }}
          longitude: >-
            {{ states.device_tracker.my_phone.attributes['longitude'] }}

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.io

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[MartinHjelmare]

Looks good!