e-wm: add git recipe with latest revision

* E19 is still in alpha stage, but I was told that many things work
  there better than old(ish) E18
* last announcement:
  https://phab.enlightenment.org/phame/live/3/post/e19_alpha2_now_with_50_more_explosions/


* but be aware that illume2 modules are gone and config mobile
  doesn't work without them
* there is new tiling config

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>