fix unresponsive chart containers

[macfarlandian]

Description of the change

Fixes a silly layout issue that I had not thought to address the first time around but is hampering development now that there are actual charts on the pages: the narrative pages now grow and shrink in width as the window is resized, and the text and chart columns stay in roughly the same proportions. The text has a maximum width, so on very large screens the charts will keep growing while the text does not. Screen real estate is more valuable for the charts at that point.

(This still doesn't implement a mobile layout but it should now look reasonable on medium-to-large screens.)

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Configuration change (adjusts configuration to achieve some end related to functionality, development, performance, or security)

Related issues

Closes #317

Checklists

Development

These boxes should be checked by the submitter prior to merging:

• Manual testing against realistic data has been performed locally

Code review

These boxes should be checked by reviewers prior to merging:

• This pull request has a descriptive title and information useful to a reviewer
• This pull request has been moved out of a Draft state, has no "Work In Progress" label, and has assigned reviewers
• Potential security implications or infrastructural changes have been considered, if relevant

[coveralls]

Pull Request Test Coverage Report for Build 513898374

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 65.31%

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Totals
Change from base Build 513889722:	0.0%
Covered Lines:	1705
Relevant Lines:	2513

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💛 - Coveralls