Include CSS Custom Property for mono font family

[joshblack]

Generated by Copilot Workspace 🤯

This pull request includes a change to the mono property of the fonts constant in the src/theme.ts file. The change adds 'var(--fontStack-monospace)' to the beginning of the font stack for monospace fonts.

[changeset-bot]

🦋 Changeset detected

Latest commit: f2c6282

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

This PR includes changesets to release 1 package

Name	Type
@primer/react	Minor

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[github-actions]

size-limit report 📦

Path	Size
dist/browser.esm.js	105.55 KB (+0.01% 🔺)
dist/browser.umd.js	106.14 KB (+0.01% 🔺)

[joshblack]

✨✨ The PR has been updated by @joshblack with changes produced using Copilot Workspace using Copilot Workspace v0.6

Topic

Add a changeset with a random name that describes these changes and tag it as a minor release

Before

• The code does not have a changeset for the pull request yet.
• The code modifies the mono font stack in src/theme.ts to use a CSS variable.

After

• The code has a changeset for the pull request in .changeset/<random-name>.md with the following content:

---
"@primer/react": minor
---
Use a CSS variable for the monospace font stack

• The code modifies the mono font stack in src/theme.ts to use a CSS variable.

[langermank]

Suggested change

	mono: fontStack([
	'var(--fontStack-monospace)',
	'SFMono-Regular',
	'Consolas',
	'Liberation Mono',
	'Menlo',
	'Courier',
	'monospace',
	]),
	mono: fontStack([
	'var(--fontStack-monospace,
	SFMono-Regular,
	Consolas,
	Liberation Mono,
	Menlo,
	Courier,
	monospace)',
	]),

I think it should be like this, but I'm not 100% sure.

[langermank]

I am now 95% sure I am wrong.

[colebemis]

Yeah, I think either version works