Drop obsolete exwm-config.el

Instead of using the obsolete exwm-config in your init.el, we recommend to
create a custom configuration tailored to your needs. The old exwm-config file
and the EXWM wiki serve as starting points. The minimal configuration to get
EXWM working is as follows:

(require 'exwm)
(setq exwm-input-global-keys `(([?\s-r] . exwm-reset)))
(exwm-enable)

In addition you may want to customize `exwm-workspace-number',
`exwm-input-global-keys' and `exwm-input-simulation-keys'. In order to rename
EXWM buffers, such that they match the window class or window title, add custom
hooks to `exwm-update-title-hook' and `exwm-update-class-hook', for example:

(add-hook 'exwm-update-class-hook
  (lambda () (exwm-workspace-rename-buffer exwm-class-name)))

* exwm-config.el: Drop obsolete file.

Author: minad