Add pull request template
Add pull request template

[ci skip]

Fixes #267.

maxogden/electron-packager,malept/electron-packager,sethlu/electron-packager,electron-userland/electron-packager,Goobaroo/electron-packager,Goobaroo/electron-packager,malept/electron-packager,electron-userland/electron-packager,sethlu/electron-packager