feat: support video footnote

config.toml

```toml
enableVideoHost = true
videoHostURL = "https://a.com/"
```

Markdown

```md
[^1]<video src="/videos/sunrise.mp4" ... title="Sunrise"></video>
```

or

```md
[^1]![](/videos/sunrise.mp4 "Sunrise")
```

Rendered HTML

```html
<p>
  <sup style="float:right" class="footnote-ref" id="fnref:1">
    <a href="#fn:1">[1]</a>
  </sup>
  <video src="https://a.com/videos/sunrise.mp4" controls></video>
  <span class="caption">◎ Sunrise</span>
</p>
```

layouts/partials/components/content.html

@@ -100,9 +100,9 @@
     {{- .Scratch.Set "Content" $Content -}}
 {{- end -}}
 
-<!-- Image Footnote -->
+<!-- Image & Video Footnote -->
 {{- $Content := .Scratch.Get "Content" -}}
-{{- $regexPatternFootnoteImage := `(<sup)(.+</sup><img)` -}}
+{{- $regexPatternFootnoteImage := `(<sup)(.+</sup><(img|video))` -}}
 {{- $regexReplacementFootnoteImage := `$1 style="float:right"$2` -}}
 {{- $Content := $Content | replaceRE $regexPatternFootnoteImage $regexReplacementFootnoteImage | safeHTML -}}
 {{- .Scratch.Set "Content" $Content -}}
@@ -135,7 +135,7 @@
 {{- $Content := $Content | replaceRE $regexPatternVideo $regexReplacementVideo | safeHTML -}}
 {{- .Scratch.Set "Content" $Content -}}
 
-<!-- Image / Video Caption -->
+<!-- Image & Video Caption -->
 {{- $Content := .Scratch.Get "Content" -}}
 {{- if .Site.Params.enableCaption -}}
     {{- $captionPrefix := .Site.Params.captionPrefix -}}