warn when `column: page` and `fig-align` are used together

[ericpgreen]

Bug description

Figures appear left aligned when setting column: page AND fig-align: center.

Originally posted here. Asked to open an issue.

Steps to reproduce

---
title: "Test"
format:
  html: 
    embed-resources: true
    smooth-scroll: true
    theme: cosmo
    fontcolor: black
    toc: true
    toc-expand: 2
    toc-title: Contents
    toc-location: left
    toc-depth: 3
    number-sections: true
    number-depth: 3
---

## Page

This aligns left to page, despite setting fig-align.

```{r}
#| label: fig-1
#| fig-cap: "A caption." 
#| column: page
#| fig-align: center

plot(mtcars)
```

## Not specified

This aligns center in main

```{r}
#| label: fig-2
#| fig-cap: "A caption." 

plot(mtcars)
```

Expected behavior

Center alignment

Actual behavior

Left alignment

Your environment

R version 4.3.2 (2023-10-31)
Platform: aarch64-apple-darwin20 (64-bit)
Running under: macOS Sonoma 14.1

Quarto check output

Quarto 1.5.56

[cscheid]

We should be emitting a warning about incompatible settings, but column: page and fig-align are not designed to be used together.

[ericpgreen]

I didn't think so, but was just trying to find a solution. Thanks @cscheid