When `table_attributes` is enabled (as it is by default for
pandoc's Markdown), attributes can be attached to a table by
including them at the end of the caption. Previously the writer
would emit an identifier in this position, but the reader didn't
handle it. Now arbitrary attributes are allowed, and they work in
both the reader and writer.
Closes#10884.
[API change]: Text.Pandoc.Extensions: Add `Ext_table_attributes`
constructor for `Extension`.
John MacFarlane
e201e3370a