Fix UV index

[caternuson]

For #9. Should hopefully get UV index reading working.

Main things done:

• Incorrect bit being set in CHLIST for enabling UV index (off by one)
• The ucoeff values were set in wrong order (datasheet is confusing on this, order determined by trial and error)
  • Values also needed to be tuples instead of ints
• Needed to force an ALS reading to update UV index value

Tested:

Adafruit CircuitPython 7.3.2 on 2022-07-20; Adafruit QT Py M0 with samd21e18
>>> import board
>>> import adafruit_si1145
>>> si = adafruit_si1145.SI1145(board.I2C())
>>> si.uv_index
0.08
>>> si.uv_index
0.78
>>> si.uv_index
5.09
>>>