Add a BibTeX citation text or link

[YanjieGao]

What would you like to be added:
Add a BibTeX citation text or link for reference
Why is this needed:
for research work citation
Without this feature, how does current nni work：
hands on write, not clear write which year?
Components that may involve changes:
document
Brief description of your proposal if any:
You could refer autokeras
https://github.com/keras-team/autokeras#cite-this-work

[kvartet]

Thank you, we have added BibTeX citation text in PR #3150, and I will close the issue.