add config-dir variable and change load-path to use it

settings/bibliography-settings.el

@@ -16,15 +16,15 @@
 
 ;;; Code:
 (use-package pdf-tools
-  :load-path "lisp/pdf-tools"
+  :load-path (lambda() (concat config-dir "lisp/pdf-tools"))
   :defer t)  ;; used by org-ref
 
 (use-package biblio
-  :load-path "lisp/biblio"
+  :load-path (lambda() (concat config-dir "lisp/biblio"))
   :defer t)  ;; used by org-ref
 
 (use-package org-ref  ;; used with some preamble defs and \printbibliography (biblatex/biber, no html export), see also ox-bibtex
-  :load-path "lisp/org-ref"
+  :load-path (lambda() (concat config-dir "lisp/org-ref"))
   :after (org)
   :defer 1
   :init