added Sensirion SHT4x humidity sensor

added Sensirion SHT4x humidity sensor

• Remove the instructional content of this template
• Provide a URL to a datasheet for the symbol(s) you are contributing

https://sensirion.com/media/documents/33FD6951/624C4357/Datasheet_SHT4x.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.

there isn't a fitting footprint, I am working on it

• If there are matching footprint PRs, provide link(s) as appropriate
• Check the output of the automated check scripts - fix any errors as required
• Give a reason behind any intentional library convention rule violation.