pass: Add config xdg specification loading

Set environment variable for pass to respect for each shell environment,
setting its pass store to the XDG_DATA_HOME directory.

pass/.config/sh/env.d/pass-xdg.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env sh
+# Make pass comply with xdg base dir specification,
+# usually password store will be found in ~/.local/share/pass
+
+export PASSWORD_STORE_DIR="$XDG_DATA_HOME/pass"