Add support for lazy loading images `loading="lazy"`

[bobbingwide]

In https://make.wordpress.org/core/2020/07/14/lazy-loading-images-in-5-5/ we can read about the WordPress support for lazy loading images.

Some of the <img> tags created by oik's shortcodes ( and blocks? ) are not automatically handled since

1. They don't include width and height attributes.
2. Nor do they include the relevant wp-image-$id class

Requirement

• Support lazy loading for the following shortcodes: [bw_logo], [bw_images], [bw_attachments], [bw_portfolio]
• Consider supporting lazy loading for: [bw_qrcode], [bw_follow_me]

Proposed solution

• [x] For [bw_logo] automatically set loading=lazy when the width and height attributes are set.
• [x] For [bw_images] change bw_force_size() to not null out the width and height values when the size is not an array.
• [x] Changes for [bw_images] will also change the output for [bw_attachments]
• [x] For [bw_portfolio] replace the retimage() call with bw_thumbnail_full( $matched_post )
• [x] While we're about it, add the syntax for the titles parameter for the [bw_images] shortcode.

pseudo code for setting "loading=lazy"

$extras = null;
if ( $width && $height ) {
   $extras = kv( "loading", "lazy);
}
$img = retimage( $classes, $url, $title, $width, $height, $extras );

[bobbingwide]

For [bw_portfolio] replace the retimage() call with bw_thumbnail_full( $matched_post )

The PHPUnit tests will need changing to cater for this change.

[bobbingwide]

The PHPUnit tests will need changing to cater for this change.

These changes were incorrectly reported against #187

Code was in v4.5.0. oik v4.7.2 now released. Closing therefore.