Text.Pandoc.Shared:
+ Remove `Element` type [API change]
+ Remove `makeHierarchicalize` [API change]
+ Add `makeSections` [API change]
+ Export `deLink` [API change]
Now that we have Divs, we can use them to represent the structure
of sections, and we don't need a special Element type.
`makeSections` reorganizes a block list, adding Divs with
class `section` around sections, and adding numbering
if needed.
This change also fixes some longstanding issues recognizing
section structure when the document contains Divs.
Closes#3057, see also #997.
All writers have been changed to use `makeSections`.
Note that in the process we have reverted the change
c1d058aeb1
made in response to #5168, which I'm not completely
sure was a good idea.
Lua modules have also been adjusted accordingly.
Existing lua filters that use `hierarchicalize` will
need to be rewritten to use `make_sections`.
