Explicitly track ws90_ver value

[bachya]

Describe what the PR does:

This PR explicitly tracks the ws90_ver value, which is the current firmware of a Wittboy 7-in-1 array.

Does this fix a specific issue?

N/A

Checklist:

• Confirm that one or more new tests are written for the new functionality.
• Run tests and ensure everything passes (with 100% test coverage).
• Update README.md with any new documentation.
• Add yourself to AUTHORS.md.

[codecov]

Codecov Report

Merging #254 (20ba09f) into dev (d4c4bf3) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 20ba09f differs from pull request most recent head eb0e494. Consider uploading reports for the commit eb0e494 to get more accurate results

@@            Coverage Diff            @@
##               dev      #254   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           21        21           
  Lines         1010      1013    +3     
=========================================
+ Hits          1010      1013    +3     

Impacted Files	Coverage Δ
ecowitt2mqtt/helpers/publisher/hass.py	100.00% <ø> (ø)
ecowitt2mqtt/const.py	100.00% <100.00%> (ø)
ecowitt2mqtt/data.py	100.00% <100.00%> (ø)

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