feat: support transform style for header

[Freddy03h]

Two related things in this PR:

• add transform in the safeStyles headerStyle
• add the safeStyles headerStyle as argument in the headerBackground function

Use case: Create a collapsible scrollview header. To migrate this use case from 4 to 5 this PR is needed but the philosophy isn't far from previous react-navigation. You need to set headerTransparent to true and use a custom headerBackground (even if don't really want a custom one).

It's needed to transform the headerBackground and the View that wrap the headerLeft/Right and the headerTitle.
Also, giving headerStyle as argument to headerBackground function make it easier to customize by setting an headerStyle option in a screen instead of recreate an entire headerBackground for each screen.

[codecov-io]

Codecov Report

Merging #158 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #158   +/-   ##
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  Coverage   93.27%   93.27%           
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  Files          36       36           
  Lines         758      758           
  Branches      191      191           
=======================================
  Hits          707      707           
  Misses         42       42           
  Partials        9        9

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[Freddy03h]

thank's for the approval