Add a symbol for WS2812B-2020 (NeoPixel Nano)

Add a derived symbol for WS2812B-2020 (NeoPixel Nano)

The footprint has been added in kicad-footprints!2896 (merged)

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Thanks for creating a pull request to contribute to the KiCad libraries! To speed up integration of your PR, please check the following items:

• Remove the instructional content of this template
• Provide a URL to a datasheet for the symbol(s) you are contributing - https://cdn-shop.adafruit.com/product-files/4684/4684_WS2812B-2020_V1.3_EN.pdf
• An example screenshot image is very helpful
• Ensure that the associated footprints match the official footprint library
  • A new fitting footprint must be submitted if the library does not yet contain one.
• If there are matching footprint PRs, provide link(s) as appropriate
• Check the output of the automated check scripts - fix any errors as required