fix(readme): build status for the develop branch

Your main development branch is `develop`.
It is usually only interesting to follow the status of the branch in development.
Of course `master` branch will almost always be passing.
Ironically, now it isn't, because our build fixes are on `develop`,
so it's another reason to switch.
Merge pull request #2925 from denis-sokolov/patch-1

fix(readme): build status for the develop branch