Improve lists(sub-lists, term)

[IdkGoodName]

Adds support for <term> tag and allows the creation of sub-lists. Em-dash(—) is used to separate the term and the description. If either of them is not present, em dash is not added.

---

<list type="number">
    <item>
        <term>A</term>
        <description>B</description>
    </item>
    <list type="bullet">
        <item><term>C</term></item>
        <item><description>D</description></item>
    </list>
    <item>E</item>
</list>

Outputs:

1. A — B
   - C
   - D
2. E

1. A — B
   • C
   • D
2. E

[Doraku]

there seems to be some conflicts, but thanks for pointing that the nested list display was not working as intended because of the Descendants instead of Elements call in the extensions! There was no need for specific code in the ListElement class as the recursion handling is automatic through the AppendAsMarkdown method (it just needed to initialize correctly the GetElementWriters of the tester and put the nested <list> inside the <item>). Still interested in the <term>!

[IdkGoodName]

I could remove the sub-list implementation and just leave out the term then

[IdkGoodName]

Should I even update this PR?

[Doraku]

Yes fell free to do it, I am done with the big refactoring and just need to add xml comments to the Api library before the next version so there shouldn't be any big conflicts from now on.

[IdkGoodName]

Sorry for basically stretching this out for a month.

[Doraku]

oh no it's me who kept making big changes with all kind of conflicts haha

[IdkGoodName]

Is it ready for merge or what does need to be changed?

[Doraku]

not sure why there's some conflict, I will try to merge it manually (sorry wasn't really available in the past weeks).

[Doraku]

Finally got around to merge it. I hope it's ok for you after rereading the microsoft documentation for list I changed a little the implementation for table (listheader should only contains terms and item only descriptions).