Add platform for Yeelight Sunflower lights

[lindsaymarkward]

Description:
Add new platform for the light component for Yeelight Sunflower bulbs (https://www.yeelight.com/en_US/product/yeelight-sunflower).

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.io#2006

Example entry for configuration.yaml:

light:
  - platform: yeelightsunflower
    host: 192.168.1.59

Checklist:

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

• Documentation added/updated in home-assistant.github.io

If the code communicates with devices, web services, or third-party tools:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• New dependencies have been added to the REQUIREMENTS variable (example).
• New dependencies are only imported inside functions that use them (example).
• New dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.
• New files were added to .coveragerc.

[mention-bot]

@lindsaymarkward, thanks for your PR! By analyzing the history of the files in this pull request, we identified @balloob, @fabaff and @robbiet480 to be potential reviewers.

[balloob]

Awesome! 🐬