Add swipedown exit fullscreen feature

[Ortes]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 20.00000% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 51.20%. Comparing base (7a4631c) to head (a56c7f0).
⚠️ Report is 14 commits behind head on master.

Files with missing lines	Patch %	Lines
lib/src/chewie_player.dart	20.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #930      +/-   ##
==========================================
- Coverage   51.21%   51.20%   -0.02%     
==========================================
  Files          25       25              
  Lines        1728     1744      +16     
==========================================
+ Hits          885      893       +8     
- Misses        843      851       +8     

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[diegotori]

Two things:

1. You need to make this configurable from the ChewieConttoller. In other words, you need to make this opt-in.
2. When making this configurable, you also need to make the threshold dismissing on swipe a configurable value, defaulting to a reasonable value.