speed up livereload

connect.reload needs a stream of files to fire, but this stream is irrelevant here and slows refresh time a lot (from ~2ms to 2000ms here)

update markdown default notes separator to ignore inline occurances of 'notes:', closes #1915, closes #2762

adds ability to override markdown plugin default options

add support for links to the id of an element nested inside slide

allow theme subfolders

fixes livereload when using root CLI param

fixes hakimel/reveal.js#3231

```js
Reveal.initialize({
    markdown: {
        defaultOptions: {
            verticalSeparator: '\n--\n`,
        }
    }
})

allows custom themes to import files from subfolders inside the `css/theme/source` folder.

in `css/theme/source/custom-theme.scss` we can now do
```scss
@import `custom-theme/controls`
@import `custom-theme/headings`
...
```

may allow perf boost

[Markdown plugin] add line number offset for code sections to markdown

Correctly strip leading white-space from markdown

* Fix overlap in overview when config.disableLayout === true

* run gulp js
after commit 9193e5cd5d6d1aa234803b753c6d032b801a8221

---------

Co-authored-by: Hakim El Hattab <hakim.elhattab@gmail.com>

add sortFragmentsOnSync option, makes it possible to avoid unwanted sorting in editing environments like slides.com

Fixes https://github.com/hakimel/reveal.js/issues/3315

If the markdown contains something that is indented by more that the
`leadingTabs`/`leadingWs` then extra white space is incorrectly removed.
ie the following example:

```
    <section data-markdown>
    some text
       indented text
          more indented text
    </section>
```

would result in the following markdown:

```
some text
   indented text
  more indented text
```

We can work around this problem by using a function to generate the
replace value.

Fixes typos

Missing lang attribute

GitHub Workflows security hardening