Document potential emacs integration support

[atuleu]

I could easily integrate jupyter_ascending with emacs with the help of an already available package code-cells. Using the, IMHO should be standard, use-package emacs configuration tool, it is only sufficient to add this code snippet to one's emacs econfiguration.

(use-package code-cells
	:mode ("\\.sync.py'" . code-cells-mode)

	:config
	(defun atu/jupyter-ascending-sync ()
		"Runs synchronization with jupyter-ascending. The synchornixation won´t  happen, if the variable atu/jupyter-sync-inhibit is non-nil"
		(interactive)
		(when (string-match-p ".sync.py\\'" (buffer-name))
			(unless atu/jupyter-sync-inhibit
				(call-process "python"
					nil nil nil
					"-m" "jupyter_ascending.requests.sync" "--filename" (buffer-file-name)
					)
				)
			)
		)

	(defun atu/jupyter-ascending-eval (start end)
		"Runs cell via jupyter-ascending or python-shell-send-region"
		(interactive)
		(if (not (string-match-p ".sync.py\\'" (buffer-name)))
			(python-shell-send-region start end)
			(setq-local atu/jupyter-sync-inhibit t)
			(save-buffer)
			(setq-local atu/jupyter-sync-inhibit nil)
			(call-process "python"
				nil nil nil
				"-m" "jupyter_ascending.requests.execute"
				"--filename" (buffer-file-name)
				"--linenumber" (number-to-string (line-number-at-pos))
				)
			)
		)

	(setq code-cells-eval-region-commands
		(mapcar (lambda (pair)
			        (if (eq (car pair) 'python-mode)
				        (cons 'python-mode 'atu/jupyter-ascending-eval)
				        pair))
			code-cells-eval-region-commands))

	:hook
	(python-mode . code-cells-mode-maybe)
	(code-cells-mode . (lambda ()
		                   (add-hook 'after-save-hook 'atu/jupyter-ascending-sync nil 'local)))
	)
                                                      

code-cells, which is compatible with jupytext provides much more functionalities, such as easy cell navigation and reordering, and native support for .ipynb files. I am not an emacs expert, so I would like not to go the path to build and package a mode to integrate this simple code, however, with the green light of this repo maintainers, I would happily contribute to jupyter_ascending's documentation in order to provide emacs community a potential integration of jupyter_ascending with emacs