Release notes and feedback page for v13

Release drafting URL: https://webschemas.org/docs/releases.html#v13

(checkbox when release notes + edits are in the main branch)

• bioschemas Bring proposed Bioschemas terms into Pending area #2862 into Pending
  • address notes in Introduce BioSchemas terms into pending #2863 (review)
• MediaReview improvements
• Product return improvements Proposal to expand support for product return policies #2880
• buyer / Org PR merged
• directApply, indicate on a JobPosting whether direct application on the same site is possible #2907
• Update schema.ttl to add PostcastSeries as expecting 'actor' property, for #2895 #2899 actors on PodcastSeries
• countryOfOrigin should be applicable to Product, CreativeWork at least. #991 - countryOf* - implemented but may need tweaks + mappings

non-vocab:

• validator
• developers page update for Clarify http/https vocabulary differences with JSON-LD #2886

Missing from previous releases

• oversight - SeekToAction domainIncludes startOffset was missing #2911 -fix oversight in SeekToAction definition (@danbri mistake in prev release).
• Add startTime and endTime to InteractionCounter #2825 InteractionCounter needs startTime, endTime. A git commit got lost somehow.

Postpone for v14 attention:

• suggest also Allow Dataset to indicate "according to specification URL" #1516 (conformsTo)
• revisit itemReviewed / review itemReviewed inverseOf review #161
• How to find current version of schema.org programmatically? #2841 (@stain suggestion)
• usability roundup - need more suggestions! Documentation Examples on BlogPosting and LiveBlogPosting Duplicate #2892