Allow to tidy attributes

[zrquan]

能否提供一个设置项，支持隐藏 #+attr_xxx: ... 这种属性行

我尝试做了些实现想提 pr，但是我 elisp 太菜了，遇到一些奇怪的 bug 无法解决——比如光标会被隐藏的属性行“挡住”不能向下移动。。。

一些修改：

(defun org-tidy--element-attr-p (e)
  (or
   (org-element-property :attr_org e)
   (org-element-property :attr_html e)))

(defun org-tidy--get-element-pos (element is-attr type)
  "Get position of TYPE from ELEMENT based on org version."
  (if (version< org-version "9.7")
      ;; 老版本使用 property
      (org-element-property type element)
    ;; 新版本使用函数
    (pcase type
      (:begin (org-element-begin element))
      (:end (if is-attr
                (org-element-contents-begin element)
              (org-element-end element)))
      (_ (org-element-property type element)))))

(defun org-tidy--element-to-ov (element)
  "Turn a single property ELEMENT into a plist for merge."
  (let* ((is-attr (org-tidy--element-attr-p element))
         (should-tidy (or (org-tidy-should-tidy element) is-attr))
         (beg (org-tidy--get-element-pos element is-attr :begin))
         (end (org-tidy--get-element-pos element is-attr :end))
         (is-top-property (= 1 beg))
         (push-ovly nil)
         (display nil))

    (pcase (list is-top-property org-tidy-top-property-style
                 org-tidy-properties-style)
      (`(t invisible ,_)
       (setq display 'empty push-ovly t))

      (`(t keep ,_) )

      (`(nil ,_ invisible)
       (setq display 'empty push-ovly t))

      (`(nil ,_ inline)
       (setq display 'inline-symbol push-ovly t))

      (`(nil ,_ fringe)
       (setq display 'fringe push-ovly t)))

    (when (and should-tidy push-ovly)
      (list :beg beg
            :end end
            :is-top-property is-top-property
            :display display))))

(defun org-tidy-buffer ()
  "Tidy."
  (interactive)
  (save-excursion
    (condition-case err
        (let* ((ast (org-element-parse-buffer))
               (raw-ovs (org-element-map ast
                           '(property-drawer drawer paragraph)
                         ......