Definition lists, attribute lists with validation, inline formatting fixes, minor code cleanup

[hmdne]

This is a working tree that supersedes #54 and https://github.com/metanorma/reverse_adoc/pull/94 .

• AttributeList support (fixes #48, fixes #42)
• DefinitionList support (fixes #37)
• Inline markup fixes (fixes metanorma/reverse_adoc#93, fixes #43)

Metanorma PR checklist

• [ ] Breaking changes (list related PRs)
• [ ] Documentation update required (create task for this)
• [ ] External dependency introduced (documentation update need)
• [ ] Gem with native library introduced

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.79%. Comparing base (defb04a) to head (f0b29dd). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #58 +/- ## ========================================== + Coverage 96.67% 98.79% +2.11% ========================================== Files 42 44 +2 Lines 1054 995 -59 ========================================== - Hits 1019 983 -36 + Misses 35 12 -23 ```

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[hmdne]

@ronaldtse This patchset is ready

[opoudjis]

This is not fixed. At all.