Add script to update showcase sites

[delucis]

This adds a script and associated weekly GitHub workflow that does the following:

1. Loads all comments in Companies & Websites Using Astro roadmap#521
2. Extracts URLs
3. Filters out URLs that don’t appear to be built with Astro (or which are already in the showcase)
4. Takes a screenshot and extracts a page title for each URL
5. Writes Markdown files to src/content/collections and resizes and saves the screenshots as WebP for each URL
6. Opens a PR documenting the sites added, and listing sites where scraping failed or which we can’t detect are built with Astro

Example PR body:

This PR is auto-generated by a GitHub action that runs every Monday to update the Astro showcase with data from GitHub and NPM.

Sites added in this PR 🆕

• midufest - ¡La fiesta de la programación!
• Showcase | Astro
• #whiteboardtheweb
• Blog - JoinGamedev - JoinGamedev
• CJ Ohanaja
• Thomas Ledoux - Home
• kainoa.us
• Portfolio | Mathias Berger--Fruhinsholz
• The Gentlemen's Agreement | My First Million
• Home - Diga Systems
• Sentral Bisnis Digital — Semangat Transformasi Digital
• Andreas Hackel
• Hong Vin Koay
• William Sjökvist
• John Zanussi
• José Aular
• Junior Jobs
• Izzi Ink Astronaut
• Sofa: Downtime Organizer - Sofa
• Connor Dowson | Portfolio
• Développement de sites web rapides et durables ! Genève, Lausanne, Annecy
• Popup builder - Fluentos
• Home | ICS Industrial
• Blacksof | Unlocking brand potential for businesses
• Safebras - Segurança que todos confiam, tranquilidade que você merece
• Gift Genius: Level Up With Unique Gift Ideas Powered by Artificial Intelligence
• St. Louis Center for Cognitive Health | Neuropsychology Clinic
• Improve Your Online Presence with Professional Profile Content

Sites that failed while scraping 🚨

These sites are new additions and appear to be built with Astro, but something went wrong while trying to scrape them. You might want to add them to the showcase manually.

• https://www.cityflo.com/

Sites that are maybe not built with Astro 🤔

We couldn’t detect that these sites were built with Astro. You might want to check manually.

https://mujs.dev/, https://ahuja-lab.in/

You can also run the script locally — pnpm update:showcase — and commit the resulting files manually.

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[tony-sull]

Very nice! Added a couple comments while I'm thinking through other reliable markers a site might be built with Astro

[tony-sull]

Excellent, thanks Chris! Very nice to have this automated for easier PR reviews 🚀