bugfix: insertion of new headline title

In the original code, if there is whitespace on the last line of the file, then
the headline will be improperly inserted *after* the whitespace.

In this bugfix, we look for `\n` as the last character of the file and add `\n`
before "* <title>" if the last character is anything else.

org-noter.el

@@ -266,7 +266,7 @@ DOCUMENT-FILE-NAME is the document filename."
               (setq notes-files-annotating notes-files)
             (with-current-buffer (find-file-noselect (car notes-files))
               (goto-char (point-max))
-              (insert (if (save-excursion (beginning-of-line) (looking-at "[[:space:]]*$")) "" "\n")
+              (insert (if (save-excursion (backward-char) (looking-at-p "\n")) "" "\n")
                       "* " document-base)
               (org-entry-put nil org-noter-property-doc-file
                              (file-relative-name document-used-path