Updated Series SEO options: OG title, Meta title and Meta description

As per title, I've updated the Search engine optimization options section with 3 new optional inputs OG title, Meta title and Meta description (as shown in the image below).

The OG title is used to set the meta property og:title and meta property twitter:title (the xf metadata_macros sets both of these via the arg-title). Basically, if you want the TITLE on Facebook/Twitter to be something different than the actual item title, then this is what this optional setting is for. If you don't set this, it uses the item title.

The Meta title input is used to set the TITLE tag for the item. If you want to use a custom title tag, this is what this is for. If you don't set a Meta title, the title of the item will be used as the TITLE tag.

The Meta description input is used to set the Meta Description tag for the Series. If you want to use a custom description for search engines, this is what this is for. If you don't set a Meta description, the description of the Series or a snippet of the Series Details will be used as the Meta Description tag.