quantization - document get_default_qconfig

[vkuzo]

📚 Documentation

See https://discuss.pytorch.org/t/get-default-qconfig-appears-in-docs-but-not-in-api-reference/103010. We should make sure this is documented and easy to discover.

cc @jerryzh168 @jianyuh @raghuramank100 @jamesr66a @jgong5 @Xia-Weiwen @leslie-fang-intel @dzhulgakov @vkuzo

[supriyar]

@jerryzh168 could you help with this for 1.8 release?

[jerryzh168]

Sure

[jerryzh168]

let's add this to https://pytorch.org/docs/master/quantization-support.html