[Feature-Request] css-classes

[nelhop]

It would be great if the vue-frame and iframe would have css-classes matching its states, as known from vue-router.

Handy classes for the vue-frame would be:

• frame-link: as general class
• frame-link-active: when the link is currently opened in the iframe

Handy classes for the iframe would be:

• frame: when the iframe is loading the content
• vue-frame-loading: when the iframe is loading the content
• vue-frame-loaded: when the content of the iframe is finished loading (similar to #13)