contrib/lisp/org-annotate-file.el: Create a customization group and convert `defvar' customization variables to `defcustom'

* contrib/lisp/org-annotate-file.el (org-annotate-file): New customization
group.

(org-annotate-file-storage-file org-annotate-file-add-search
org-annotate-file-always-open): Convert `defvar' symbols to `defcustom' using the new group.

contrib/lisp/org-annotate-file.el

@@ -59,14 +59,24 @@
 
 (require 'org)
 
-(defvar org-annotate-file-storage-file "~/.org-annotate-file.org"
-  "File in which to keep annotations.")
-
-(defvar org-annotate-file-add-search nil
-  "If non-nil, add a link as a second level to the actual file location.")
-
-(defvar org-annotate-file-always-open t
-  "If non-nil, always expand the full tree when visiting the annotation file.")
+(defgroup org-annotate-file nil
+  "Org Annotate"
+  :group 'org)
+
+(defcustom org-annotate-file-storage-file "~/.org-annotate-file.org"
+  "File in which to keep annotations."
+  :group 'org-annotate-file
+  :type 'file)
+
+(defcustom org-annotate-file-add-search nil
+  "If non-nil, add a link as a second level to the actual file location."
+  :group 'org-annotate-file
+  :type 'boolean)
+
+(defcustom org-annotate-file-always-open t
+  "If non-nil, always expand the full tree when visiting the annotation file."
+  :group 'org-annotate-file
+  :type 'boolean)
 
 (defun org-annotate-file-ellipsify-desc (string &optional after)
   "Return shortened STRING with appended ellipsis.