Disable tabbing on read only fields

[gregbty]

This disables tabbing on read only fields so that they don't trigger things like validation by exposing a new tabIndex prop.

[codecov]

Codecov Report

Merging #96 into master will increase coverage by 0.01%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master      #96      +/-   ##
==========================================
+ Coverage   46.87%   46.88%   +0.01%     
==========================================
  Files          54       54              
  Lines        1681     1687       +6     
  Branches      304      308       +4     
==========================================
+ Hits          788      791       +3     
- Misses        828      831       +3     
  Partials       65       65

Impacted Files	Coverage Δ
...ld-host-renderer/field-host-renderer.component.tsx	16.35% <33.33%> (+0.76%)	⬆️

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