Create pagebreak from inline command too

[cderv]

This is a try to making some evolution to pandoc pagebreak lua filter in the aim of supporting inline command. Supporting this would fix #1752.

Initially the pagebreak lua filter was added from pandoc lua filters repo and support \newpage or \pagebreak command as its own paragraph. It would detect this paragraph and replace it with a RawBlock with the correct pagebreak syntax.

This PR is to see if we can detect one of the command in the paragraph itself and replace it by RawInline.

It seems to works well for docx output. This need to be thoroughly tested for other format.

This is a draft PR to share this and test it.

[atusy]

Thanks a lot for the quick replies and PR! And excuse my slow action...

I upvote to activate RawInline insertion for limited formats because it sounds safer.
I also tried ODT, and it also adds a paragraph with a blank line.

[yihui]

You don't need to test all formats. I'm okay if it also works for HTML, LaTeX, and ODT. I can also merge the PR as is if you don't want or don't have time to test these formats. Thank you!

BTW, when you are done, please add a NEWS item.

[cderv]

The PR was still draft as I was waiting for it to be tested by @atusy.
I will test further to undraft it so that it could be merged.

[cderv]

I decided to leave it only for DOCX and ODT. The commands are tex anyway so it is ok for pdf.
For HTML, I am not sure adding a pagebreak (<div style="page-break-after: always;"></div>) inside a paragraph (<p><\p>) is something valid, even if browser seems to deal with it. So it will be ignored, and only work in HTML if \newpage or \pagebreak is in its own paragraph.

@atusy You can can know retest that everything is ok with this PR now it is done. Thanks !

[cderv]

@atusy did you have a chance to look at it yet ?

[atusy]

@cderv Oops, I'm sorry I have totally missed your mention.
I'll check it tomorrow morning.

[atusy]

@cderv
As far as I tried, it adds a blank line at the beginning of the new page. Does it happen to you?

[cderv]

Yes I got the same you're right.

I think come from the blank line in the Rmd file just after \newpage.

---
output:
  word_document:
    md_extensions: "+hard_line_breaks"
---

Newpage juste after this line.\newpage

This is on a new page with a blank line before

But if you don't put it, the docx file is corrupted 🤔

---
output:
  word_document:
    md_extensions: "+hard_line_breaks"
---

Newpage just after this line.\newpage
This is on a new page 

This need to be improved ... if it can. I am not sure of the openxml raw code to add here.

I'll look into it. Thank you for your test !