Adds row support to uniforms-material RadioField

[asibilia]

Since RadioField is using Material's RadioGroup this change would allow users to specify the row property for the group (changing the orientation from vertical to horizontal).

From Material's RadioGroup API:

To lay out the buttons horizontally, set the row prop: .

[codecov]

Codecov Report

Merging #834 (d752e7b) into master (27681eb) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #834   +/-   ##
=======================================
  Coverage   97.54%   97.54%           
=======================================
  Files         175      175           
  Lines        3419     3420    +1     
  Branches      659      658    -1     
=======================================
+ Hits         3335     3336    +1     
  Misses          8        8           
  Partials       76       76           

Impacted Files	Coverage Δ
packages/uniforms-material/src/RadioField.tsx	89.28% <100.00%> (+0.39%)	⬆️
packages/uniforms/src/BaseForm.tsx	96.42% <0.00%> (ø)

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[radekmie]

Thanks, @asibilia! I've added two minor requests.