Chainguard feed announcement blog post (#2328)

This is good enough for publication as-is, but can be enhanced with a
cross-link to Chainguard's corresponding blog post

---------

Co-authored-by: Xueqin Cui <[email protected]>
Co-authored-by: Holly Gong <[email protected]>

gcp/appengine/blog/content/posts/announcing-chainguard.md

@@ -0,0 +1,15 @@
+---
+title: "Chainguard adds OSV feed"
+date: 2024-07-02T16:00:00Z
+draft: false
+author: OSV Team
+---
+
+Chainguard has recently started [publishing their security advisories in OSV](http://www.chainguard.dev/unchained/chainguard-enhances-security-with-osv-advisory-feed), and these are now feeding into the OSV.dev database. This expands OSV.dev’s coverage of Linux distributions, by including security advisories for [Wolfi](https://www.chainguard.dev/unchained/introducing-wolfi-the-first-linux-un-distro).
+<!--more-->
+
+This data source addition is particularly noteworthy, as it makes a direct contribution to the comprehensiveness of using OSV.dev as the data foundation for comprehensive container image scanning, an [area of focus](https://github.com/google/osv-scanner/issues/64) for the team this year.
+
+If you are interested in working with us to contribute vulnerability data to
+OSV.dev, please get in touch. Details of the process are available
+[here](https://github.com/google/osv.dev/blob/master/CONTRIBUTING.md#contributing-data).