Updates to Emacs preferences

- Prefers "$HOME" to "~/urbint" for current project
- Prefers dark colorscheme
- Allows source-jumping to Emacs (nixify this to remove dep on
  path/to/source)

configs/shared/emacs/.emacs.d/snippets/c-mode/struct

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: struct
+# key: struct
+# --
+typedef struct $1 {
+  $2
+} $1_t;