Add EmDash CMS guide stub

[danielmlr]

Description (required)

This PR adds a stub page for EmDash, an open-source CMS built specifically for Astro, to the CMS guides. It follows the process for new Astro + X guides.

The stub consists of:

• src/content/docs/en/guides/cms/emdash.mdx with a one-line description and two official links
• the official EmDash logo as an optimized SVG in public/logos/, registered in src/data/logos.ts

Drafted and reviewed with Claude Fable 5 (separate sessions).

[astrobot-houston]

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Tracked Files

File	Note
en/guides/cms/emdash.mdx	Localization added, will be marked as complete.

Warnings reference

Icon	Description
🔄️	The source for this localization has been updated since the creation of this pull request, make sure all changes in the source have been applied.

[github-actions]

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✅ Deployment complete!

• Latest commit: 69d81e3
• Preview: https://add-emdash-cms-stub.previews.docs.astro.build
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[ArmandPhilippot]

Thank you; I think it makes sense to add EmDash here! I left a nit for consistency. Otherwise, this LGTM.

Fortunately, EmDash creator is an Astro core maintainer 😄 so, I ping @ascorbic, at least to inform him and, if he wishes, to check if the introductory sentence suits him. And I'll wait a bit before merging this.

[ArmandPhilippot]

Thanks, again! 🫡