Add stackoverflow to issue template (#1290)
Add stackoverflow to issue template (#1290)

## What does this PR do ?

Edit the Issue template to incite users to use Stackoverflow for questions.  
Also add more explicit context description.  

If this PR is merged, I will use the same template for all our repositories 
kuzzleio/kuzzle,kuzzleio/kuzzle,kuzzleio/kuzzle,kuzzleio/kuzzle