Support for `renderDimensionAttributes`, `width`, `height`, and `format` resp. `formats`

Lazybones will now render width, height and src attribures whenever dimension are defined and thus help to prevent content reflow after image loading. The src contains an svg data-uri with the image dimensions. This can be controlled via renderDimensionAttributes.

Sitegeist.Lazybones:Picture:

• renderDimensionAttributes: render dimension attributes (width/height) for the img-tag when the data is available from the imageSource
  if not specified dimensions will be enabled automatically for pictures that only use the formats options.
• width: (optional) the base width, will be applied to the imageSource
• height: (optional) the base height, will be applied to the imageSource
• formats: image formats that will be rendered as sources of separate type (string or array)

Sitegeist.Lazybones:Image:

• renderDimensionAttributes: render dimension attributes (width/height) when the data is available from the imageSource. Enabled by default.
• width: (optional) the base width, will be applied to the imageSource
• height: (optional) the base height, will be applied to the imageSource
• format: the image-format for the source like webp or png, is applied to imageSource and type

When renderDimensionAttributes is enabled and the data is available the img-tag will also render an empty inline svg-src with the required dimensions as placeholder to prevent layouts shifting after loading.

Sitegeist.Lazybones:Source:

• format: the image-format for the source like webp or png, is applied to imageSource and type
• width: (optional) the base width, will be applied to the imageSource
• height: (optional) the base height, will be applied to the imageSource

In addition all Sitegeist.Lazybones:Source elements rendered inside of a Sitegeist.Lazybones:Picture will inherit the values imageSource, srcset and sizes. Also Source no longer renders data-sizes attributes which are ignored by lazysizes instead sizes are rendered directly.