Add an optional "title" attribute to the iframe in the vimeo shortcode. If one is not given, the title attribute will default to "vimeo video". It is imperative for iframes to have a non-empty "title" attribute in order to meet WCAG2.0 accessibility guidelines https://www.w3.org/TR/WCAG20-TECHS/H64.
This means that you now can do:
{{< vidur 9KvBeKu false true 32 3.14 >}}
And the boolean and numeric values will be converted to `bool`, `int` and `float64`.
If you want these to be strings, they must be quoted:
{{< vidur 9KvBeKu "false" "true" "32" "3.14" >}}
Fixes#6371
The `safeHTMLAttr` function operates on a full attribute definition, not
just within the attribute value.
Docs: https://gohugo.io/functions/safehtmlattr/
For `opengraph.html`, run the whole `content` HTML attribute through
`safeHTMLAttr`. That will preserve `+` signs in formatted dates.
For `vimeo_simple.html`, `safeHTMLAttr` was in the context of an
attribute value, thus having no effect. In this case we could replace it
with `safeURL`, but since the code is coming from an API it is safer to
just let Go's template engine sanitize the value as it already does with
`provider_url`.
Fixes#5236 (no need to change Go upstream)
Related to #5246
Having them in separate files should make maintainance easier.
When adding new or making changes to the templates:
```bash
mage generate
```
This will get the Go code in sync.
Fixes#4457
