Add SHT20

[tyeth]

This is untested, awaiting feedback on adafruit/Wippersnapper_Components#97

[brentru]

Hey @tyeth - @lorennorman added a new feature that we're going to document in a bit, this is the perfect PR to test on.

We've added a new field ("published":true) to WipperSnapper component definitions that have been added and released with a new firmware version of WipperSnapper.

To test, once the component def. is pulled in...

In components, check the "show dev" box

then, find the SHT20 component for testing

Test it out and post a screenshot here!

[tyeth]

Hey this is brilliant, unfortunately I haven't got the SHT20 (I'll still do the change for fahrenheit), could try tomorrow with the VL53L0X if that works with the preview components?
-Edit- Just updated one and see the board (vl53l0x) when I enable dev, wicked. I'll plug it in tomorrow

[brentru]

@tyeth Did you get a SHT20 in for testing?

[tyeth]

no @brentru sorry, they were all out of stock or expensive locally so ordered from China, couple of weeks before I can test. I can stick it back to draft if preferred

[brentru]

Sure - let's mark this as a draft until ready!

[brentru]

@tyeth checking in on the status of this PR

[tyeth]

my sensors are stuck in china, not sure if being reposted or got to buy more, stalled sorry.

[brentru]

no problem - it's almost CNY

[tyeth]

I'm culling this PR as the board works with Si7021 driver. New PR #409