v1.3.3.4: support pip installation with cuda extensions

add BASICSR_EXT env

V1.3.3.1

version 1.3.3

version 1.3.2

🔖 VERSION 1.2.0

🔖 VERSION 1.1.1

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🔖 VERSION 1.1.0

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Merge branch 'master' of github.com:xinntao/BasicSR

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