work on update functions

[maelle]

The plan is for me to use this branch when working on the dev guide release @mpadge.

The big limitations of both update functions is that

• they rely on the XML structure to be the same to start with. So we can't split a paragraph in a translation or add a translation note outside of the paragraph.
• re-use nodes like paragraphs, lists. In lists we might want to re-use items!
• re-write the whole file with tinkr. Maybe we should instead do a bit of surgery on the file to prevent the reformatting changes in the Git diff.

One thing that might help is adding a function deepl_translate_clipboard() that would just take source and target language, and use the config file. At least I know it would help me.