Add list section to web hierarchy section

[nataliafitzgerald]

Adds bulleted lists, numbered lists, nested lists, and link lists to the DM.

Additions

• Bulleted lists
• Numbered lists
• Nested lists (bulleted)
• Nested lists (numbered)
• Link lists

Removals

-

Changes

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Testing

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Review

• @marteki @Scotchester @jimmynotjim

Preview this PR without the whitespace changes

Screenshots

Notes

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Todos

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Checklist

• [ ] Changes are limited to a single goal (no scope creep)
• [ ] Code can be automatically merged (no conflicts)
• [ ] Code follows the standards laid out in the front end playbook
• [ ] Passes all existing automated tests
• [ ] New functions include new tests
• [ ] New functions are documented (with a description, list of inputs, and expected output)
• [ ] Placeholder code is flagged
• [ ] Visually tested in supported browsers and devices
• [ ] Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)

[Scotchester]

A few questions/comments:

1. Similar to what I suggested to Jimmy in the Capital Framework docs, is it necessary to break out the nested styles into separate sections, or could we just include a nested list within each of the main list sections?
2. Is it worth showing a nested numbered list? (I.e., an example where both parent and child lists are numbered.)
3. The "16px / 8px" is somewhat confusing to me. Typically that kind of construction would represent type size / leading, but the 8px here is intended to represent the extra margin between list items, correct? I think it'd be good to be more explicit about that.

[nataliafitzgerald]

@Scotchester I've captured your recommendations and will submit a separate PR next week to address them. I think your points 1 and 3 make sense. In terms of including the nested numbered list, I can certainly include it but I haven't seen a use case for this in our content. Have you? I just want to make sure that the patterns we're including are something we'd want people to use.

Do you feel comfortable with merging what we have here as a first step?