Add guide for PR title  (#3936)
Add guide for PR title  (#3936)

* update PR guide for a better release log

* detail on pr title. and fix typo

leemotive/vue,Kingwl/vue,leemotive/vue,Hanks10100/vue,pramudaprakash/GITHUB,optimizely/vue,Kingwl/vue,Jinjiang/vue,Ddder-FE/vue,Jinjiang/vue,hanhongyuan/vue,xueyaodeai/vue,wushuyi/vue,KingMario/vue,Ddder-FE/vue,Ddder-FE/vue,Hanks10100/vue,cnchanning/vue,KingMario/vue,vuejs/vue,hanhongyuan/vue,KingMario/vue,KingMario/vue,hanhongyuan/vue,pramudaprakash/GITHUB,gebilaoxiong/vue,greennyreborn/vue,xueyaodeai/vue,Hanks10100/vue,vuejs/vue,Hanks10100/vue,greennyreborn/vue,xueyaodeai/vue,cnchanning/vue,lizhiyao/vue,gebilaoxiong/vue,Jinjiang/vue,cnchanning/vue,wushuyi/vue,leemotive/vue,Kingwl/vue,vuejs/vue,lizhiyao/vue,pramudaprakash/GITHUB,lizhiyao/vue,Jinjiang/vue,sreesirisha/GITMidtermexam,hanhongyuan/vue,vuejs/vue,Kingwl/vue,greennyreborn/vue,Ddder-FE/vue,xueyaodeai/vue,sreesirisha/GITMidtermexam,sreesirisha/GITMidtermexam,lizhiyao/vue,leemotive/vue,greennyreborn/vue,pramudaprakash/GITHUB,sreesirisha/GITMidtermexam,gebilaoxiong/vue