Add my-org-insert-structure-template

At the time of writing, the Gitea org mode parser cannot handle lower case
org-mode structure blocks, which breaks display of org files in the web
interface.

Should be fixed when issue go-gitea/gitea#5710 is
resolved.

As a workaround, simply make sure the structure blocks are upper case (which
they used to be before org-mode 9.2).

configuration.org

@@ -830,6 +830,7 @@ keeping track of time spent at work.
            ("C-c t" . my-org-todo-list)
            :map org-mode-map
            ("C-c '" . my-org-edit-special)
+           ([remap org-insert-structure-template] . my-org-insert-structure-template)
            ("M-p"   . org-previous-visible-heading)
            ("M-n"   . org-next-visible-heading))
 
@@ -882,6 +883,15 @@ keeping track of time spent at work.
 
     (evil-define-key 'insert org-mode-map [tab] 'org-cycle)
 
+    (defun my-org-insert-structure-template ()
+      "Like `org-insert-structure-template', but upcase all org block structures in current buffer."
+      (interactive)
+      (call-interactively #'org-insert-structure-template)
+      (save-excursion
+        (goto-char (point-min))
+        (while (re-search-forward "#\\+\\(begin\\|end\\)_[[:alnum:]]+" nil t)
+          (replace-match (upcase (match-string 0))))))
+
     (defun my-org-todo-list ()
       "Show org-todo-list with \"IN PROGRESS\" keyword selected."
       (interactive)