Create the "How To Submit Event" page

@sirodoht create the *How To Submit Event*  page on this repository.

Source from skgtech: https://github.com/skgtech/skgtech.github.io/blob/master/submit-event/index.md

Position in `front/templates/city/how-to-submit.jade`, and edit add proper routes on the [city specific route file](https://github.com/WeAreTech/wearetech.io/blob/master/back/routes/city.router.js).