Minor fixes for packaging

* .gitignore: Add ELPA files.
* exwm-workspace.el: Autoload exwm-workspace-switch.
* README.org: Renamed from README.md; add an installation note.

README.md

@@ -1,13 +0,0 @@
-Emacs X Window Manager
-======================
-
-EXWM (Emacs X Window Manager) is a full-featured tiling X window manager for
-Emacs built on top of [XELB](https://github.com/ch11ng/xelb).
-It features:
-+ Fully keyboard-driven operation
-+ Hybrid layout modes (tiling & stacking)
-+ Workspace support
-+ ICCCM/EWMH compliance
-+ Basic RandR support (optional)
-
-Please check the [wiki](https://github.com/ch11ng/exwm/wiki) for more details.