fix(v2): make doc container full width when hidden sidebar

[lex111]

Motivation

PR #4241 was merged too quickly so I didn't have time to test it as it introduced a small regression for collapsible doc sidebar.

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

Before	After (centered)

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.)

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⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟠 Performance	65
🟢 Accessibility	96
🟢 Best practices	100
🟢 SEO	100
🟢 PWA	95

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Size Change: +14 B (0%)

Total Size: 158 kB

ℹ️ View Unchanged

Filename	Size	Change
website/build/assets/css/styles.********.css	17.6 kB	0 B
website/build/assets/js/main.********.js	111 kB	+15 B (0%)
website/build/blog/2017/12/14/introducing-docusaurus/index.html	21.7 kB	0 B
website/build/docs/introduction/index.html	180 B	0 B
website/build/index.html	6.95 kB	-1 B (0%)

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[slorber]

oh, I see 😓 that's annoying

Not a big deal but the scrollbar appears during the collapsing anim. Wonder if there's an easy way to fix this properly.

Otherwise we can merge this and see later, that does not have a too annoying impact

[slorber]

will merge this for now but if you have a better solution we can revisit

[lex111]

Not a big deal but the scrollbar appears during the collapsing anim. Wonder if there's an easy way to fix this properly.

Maybe we can solve this issue if we set the maximum width for code blocks only. How do you like this idea?

[slorber]

Not sure, as long as the solution is not too complex and does not involve too much complex calc maths that would likely break over time, open for any suggestion :)