Update lightning logo (#4490)
Update lightning logo (#4490)

* docs logo

* use png

* cleaning

* vectorial

* icon

* icon

* use png

* cleaning

* aync

Co-authored-by: Jirka Borovec <70dd9eb887c50aeab51965d6105969353f15a078@pytorchlightning.ai>
Co-authored-by: Sean Naren <38c2a72b51bd16985657dd1bba52c86a84e72a32@gmail.com>
Co-authored-by: chaton <5f50a84c1fa3bcff146405017f36aec1a10a9e38@grid.ai>
williamFalcon/pytorch-lightning,williamFalcon/pytorch-lightning