Initial import of Template:CustomEventProperties
Initial import of Template:CustomEventProperties

https://developer.mozilla.org/en-US/docs/Template:CustomEventProperties

Contributors (by MDN username):
* BychekRU
* chrisdavidmills
* ethertank
* Jeremie

a2sheppy/kumascript,jpmedley/kumascript,a2sheppy/kumascript,jpmedley/kumascript