add thrid party login -- GitHub and LinkedIn#496

Merged

jdneo merged 13 commits intoLeetCode-OpenSource:masterfrom

yihong0618:master

Jan 12, 2020

Commits on Dec 3, 2019

Commits on Dec 4, 2019

Commits on Dec 5, 2019

fix preposition typo
yihong0618
committed

Commits on Dec 20, 2019

Commits on Dec 27, 2019

Commits on Dec 29, 2019

make naming more formal by review
yihong0618
committed

Commits on Jan 8, 2020

add two-factor support for GitHub login
yihong0618
committed