Add details on Debian and Alpine sources to README.md (#929)

Author: oliverchang

README.md

@@ -45,6 +45,13 @@ The following ecosystems have vulnerabilities encoded in this format:
     ([CC0 1.0](https://github.com/cloudsecurityalliance/gsd-database/blob/main/LICENSE))
 -   [OSS-Fuzz](https://github.com/google/oss-fuzz-vulns)
     ([CC-BY 4.0](https://github.com/google/oss-fuzz-vulns/blob/main/LICENSE))
+    
+Additionally, the OSV.dev team maintains a conversion pipeline for:
+
+- [Debian Security Advisories](https://storage.googleapis.com/debian-osv/index.html),
+  using the conversion tools [here](https://github.com/ossf/osv-schema/tree/main/tools/debian).
+- [Alpine SecDB](https://storage.googleapis.com/cve-osv-conversion/index.html?prefix=osv-output/),
+  using the conversion tools [here](https://github.com/google/osv.dev/tree/master/vulnfeeds/cmd/alpine).
 
 Together, these include vulnerabilities from: