Add missing Inline and Block AST elements

[rnwst]

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Constructors for Inline and Block elements were missing the LineBlock and Underline elements. The constructors now match with the elements listed at https://hackage.haskell.org/package/pandoc-types-1.22.2.1/docs/Text-Pandoc-Definition.html.

[jgm]

Not sure why CI is failing. We can try rerunning later.

[ickc]

The CI has been acting up to me lately.

I am quite busy at the moment so I am sorry I won't have time to look at it soon. I'll come back to this later.

[sergiocorreia]

The CI has been acting up to me lately.

I am quite busy at the moment so I am sorry I won't have time to look at it soon. I'll come back to this later.

Possibly related, but I had to tweak the panflute CI code due to a change in how github.com distributes the assets (particularly, pandoc): https://github.com/sergiocorreia/panflute/commit/b1fcddfa

[ickc]

Very likely to be this, it starts acting up around 2 weeks ago.

When I first set up the logic like that, it is pre-github actions era. When I have the time I'd refactor it into a GitHub Action perhaps and so that we can fix any future problems in one single place.

[ickc]

Actually someone already did that: https://github.com/marketplace/actions/setup-pandoc

I'll try to use it in other repositories first and if it works well propagate here.