fix: height option for Code field

[mihaimdm22]

Instead of rows and auto I thought about implementing a height option that will enforce the size of the field(if specified), otherwise it defaults to auto and the size will fit all content. I think it will be easier for the administrator to configure and also makes sense to default to auto. Let me know what you think about this.

[codecov]

Codecov Report

Merging #179 into master will increase coverage by 0.56%.
The diff coverage is 94.23%.

@@            Coverage Diff             @@
##           master     #179      +/-   ##
==========================================
+ Coverage   96.03%   96.59%   +0.56%     
==========================================
  Files          87      130      +43     
  Lines        1890     3551    +1661     
==========================================
+ Hits         1815     3430    +1615     
- Misses         75      121      +46     

Impacted Files	Coverage Δ
lib/avo/app/tools_manager.rb	50.00% <50.00%> (ø)
spec/dummy/app/policies/user_policy.rb	56.25% <53.33%> (ø)
spec/dummy/app/avo/filters/published_filter.rb	66.66% <66.66%> (ø)
lib/avo/app/action.rb	80.00% <80.00%> (ø)
lib/avo/engine.rb	85.71% <85.71%> (ø)
lib/avo/app/fields/boolean_field.rb	93.75% <87.50%> (ø)
lib/avo/app/app.rb	89.70% <89.70%> (ø)
lib/avo/app/fields/key_value_field.rb	90.90% <90.90%> (ø)
.../avo/app/fields/field_extensions/has_field_name.rb	91.66% <91.66%> (ø)
...lds/field_extensions/visible_in_different_views.rb	92.85% <92.85%> (ø)
... and 170 more

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[adrianthedev]

GG!

Pushed the same change to show view too!