Add grid-template-columns to<CardGrid>

[delucis]

Description

• This PR adds a base grid-template-columns rule to the <CardGrid> component to apply on smaller screens as one 100% wide column.

• This helps avoid overflow when there is complex content inside the grid children. We already apply this rule as an override in Astro Docs to avoid overflow, but I only just remembered to upstream this.

• Why can this be an issue? Without an explicit column width, the grid uses an implicit width based on context. For example, without this rule, cards on the Astro Docs homepage would overflow due to the code block in the “Start a new project” card:

  

• Adding an explicit column width avoids that and ensures children are constrained as expected:

  

[changeset-bot]

🦋 Changeset detected

Latest commit: 1cccb5b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@astrojs/starlight	Patch

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[astrobot-houston]

size-limit report 📦

Path	Size
/index.html	6.15 KB (+0.1% 🔺)
/_astro/*.js	22.41 KB (0%)
/_astro/*.css	13.73 KB (0%)