feat: Link back to support article for older models

Author: jacobgkau

src/archive.md

@@ -71,6 +71,10 @@ The source can be viewed [on GitHub](https://github.com/system76/tech-docs).
 - [Thelio Mira (thelio-mira-r1.0)](models/thelio-mira-r1.0/README.md)
 - [Thelio Spark (thelio-spark-b1-n2)](models/thelio-spark-b1-n2/README.md)
 
+## Previous Models Not in Tech Docs
+
+Some older models that aren't listed on the Tech Docs website have quickstart guides or service manuals available on the [System76 Support website](https://support.system76.com/articles/guides).
+
 ## Current Models
 
 See [Current Models](README.md).