modified_time and published_time are not propagated to their og/acticle counterparts

[tripodsan]

Description

1. according to:
   

   helix-html-pipeline/src/steps/extract-metadata.js

   Lines 269 to 273 in f112f14

   	'og:updated_time': meta.modified_time,
   	'article:tag': meta.tags || [],
   	'article:section': meta.section,
   	'article:published_time': meta.published_time,
   	'article:modified_time': meta.modified_time,

modified_time and published_time should be propagated to og:updated_time etc, but this doesn't work.

2. the modified_time (and maybe also published_time) could be calculated automatically based on the documents source modification time (and published time). but this would introduce a major change the meta-data headers

3. rename to modified-time and published-time to be more consistent with other metadata