fix(v2): fix warning and improve styling inline TOC

[lex111]

Motivation

Currently, when going on Configuration page in dv mode, we get a couple of warnings:

Warning: validateDOMNesting(...): <ul> cannot appear as a descendant of <p>.
Warning: validateDOMNesting(...): <div> cannot appear as a descendant of <p>.

This is because only inline elements should be inside the p tag. Unfortunately, this cannot be solved by anything other than placing the TOCInline component on a new line.

I also decided to restyle the inline TOC as a regular list because it doesn't look very good right now.

Before	After

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

Preview.

Related PRs

(If this PR adds or changes functionality, please take some time to update the docs at https://github.com/facebook/docusaurus, and link to your PR here.)

[netlify]

[V1] Deploy preview success

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Deploy preview for docusaurus-2 ready!

Built with commit c59b149

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[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟠 Performance	52
🟢 Accessibility	99
🟢 Best practices	100
🟢 SEO	100
🟢 PWA	95

Lighthouse ran on https://deploy-preview-4163--docusaurus-2.netlify.app/classic/

[github-actions]

Size Change: +15 B (0%)

Total Size: 156 kB

ℹ️ View Unchanged

Filename	Size	Change
website/build/assets/css/styles.********.css	17.7 kB	0 B
website/build/assets/js/main.********.js	109 kB	+14 B (0%)
website/build/blog/2017/12/14/introducing-docusaurus/index.html	21.7 kB	+1 B (0%)
website/build/docs/introduction/index.html	180 B	0 B
website/build/index.html	6.96 kB	0 B

_{compressed-size-action}

[slorber]

thanks, looks better