feat: add children prop to tab bar indicator component

[grezxune]

Motivation

I want to be able to display a <LinearGradient/> component inside the <TabBarIndicator/>. While you can use the renderIndicator prop on TabBar, you cannot render a wrapper or child of the indicator and have it inherit the animation the library already provides. By providing a children option to TabBarIndicator, this problem is easily solved.

Test plan

Tests all still pass and to test this specific change, try something like this:

<TabBar
  renderIndicator={(props) => {
    return (
      <TabBarIndicator {...props}>
        {someChildComponent}
      </TabBarIndicator>
    )
  }}
/>

This allows more complex components to be animated and accurately denote the active tab. I have some screenshots of an example where I'm using a <LinearGradient/> container to display a gradient indicator - something not possible with just a style object.

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[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (bd96d89) 75.78% compared to head (3da179e) 75.78%.

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Additional details and impacted files

@@           Coverage Diff           @@
##             main   #11566   +/-   ##
=======================================
  Coverage   75.78%   75.78%           
=======================================
  Files         196      196           
  Lines        5789     5789           
  Branches     2267     2267           
=======================================
  Hits         4387     4387           
  Misses       1355     1355           
  Partials       47       47           

Files Changed	Coverage Δ
...ages/react-native-tab-view/src/TabBarIndicator.tsx	48.97% <ø> (ø)

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[osdnk]

looks nice! Thanks

I guess it wasn't supported earlier as there was no deep motivation, but it looks like you found one :)