### Bug description

This relates to discussion in https://github.com/quarto-dev/quarto-cli/discussions/825 and comment in https://github.com/quarto-dev/quarto-cli/issues/1391#issuecomment-1186148935

When a custom footer is set to 
````yaml
format: 
  revealjs:
    footer: Custom footer
````

It is possible to hide it on a specific slide using the trick of inserting an empty slide footer

````
# Slide 2

content 

::: footer
:::
````

However, this does not work on first slide at first
````markdown
---
format: 
  revealjs:
    footer: Custom footer
---

# Slide 1 

content

::: footer
:::

# Slide 2

content 
````

This is because the feature (or free riding feature) rely on the per side footer overwrite using a `slidechanged` event which does not happen when presentation is loaded first time
https://github.com/quarto-dev/quarto-cli/blob/763b0ed7f060b206ef9b3a247612126b5f2f1f2a/src/resources/formats/revealjs/plugins/support/support.js#L117-L133

This means that in the example above if you go to slide 2 then back to slide 1, it will hide the footer. 

Hiding footer on title slide can be useful when you want to do a custom one like in https://github.com/quarto-dev/quarto-cli/issues/1391#issuecomment-1186148935 example (https://github.com/giabaio/quarto-slides/blob/main/assets/title-slide.qmd)


Having a real mechanism to hide a footer (like adding `.no-footer` class on a slide maybe ?) would be a plus


2022-07-18T09:20:57Z
cderv
enhancement revealjs
Future
open
[FR] Ability to hide footer on specific slides including title-slide
https://github.com/quarto-dev/quarto-cli/issues/1445