Update Readme

[ADataDate]

-update readme to include new makecode site
-delete comment about where to place the "startweatheronitoring" block - this is now fixed.
-remove beta tags

[bboyho]

It looks like the README.md has been updated and the start weather monitoring package is issue is fixed. The issues related will be closed:

• Possible fix for "start weather monitoring" not working in "on start" block #13
• Temperature doesn't change while program is running #11

However, the "Beta" tag still showing up when you try to Add Package... > weather-bit in MakeCode.