Add some implementations and systems

Author: patzielinski

content/en/docs/getting-started.md

@@ -20,22 +20,40 @@ for any TUF adoption.
 TUF implementations provide libraries implementing the primitives and
 algorithms, such as the detailed client workflow, in the specification.
 
-- [python-tuf](https://github.com/theupdateframework/python-tuf), the reference
-  implementation
+### Reference implementations
+
+- [python-tuf](https://github.com/theupdateframework/python-tuf)
 - [go-tuf](https://github.com/theupdateframework/go-tuf/)
 - [tuf-js](https://github.com/theupdateframework/tuf-js)
+- [rust-tuf](https://github.com/theupdateframework/rust-tuf)
+
+### Third-party implementations
+
+- [php-tuf](https://github.com/php-tuf/php-tuf)
+- [tough](https://github.com/awslabs/tough), by AWS Labs
+- [Notary Project](https://github.com/notaryproject/notary), by the Notary
+  Project
 
 ## Systems
 
 TUF systems build on top of library implementations and provide opinionated
 signing systems designed for particular use-cases.
 
+### Current Systems
+
 - [Repository Service for TUF](https://repository-service-tuf.readthedocs.io/en/stable/)
   (RSTUF) is a designed to integrate into an existing artifact repository with
   an established storage and delivery system.
 - [tuf-on-ci](https://github.com/theupdateframework/tuf-on-ci/) is a TUF
   repository and signing tool designed to operate on a CI system and guide
   signing events through Git forge workflows.
+- [Uptane](https://uptane.org/) enables secure software updates for automobiles.
+- [The Archive Framework](https://github.com/openlawlibrary/taf) (TAF) is a
+  framework that aims to provide archival authentication and ensure that Git
+  repositories can be securely cloned/updated.
+- [TUF Browser](https://github.com/freedomofpress/tuf-browser), from the Freedom
+  of the Press Foundation, is a minimal TypeScript implementation of TUF
+  intended to be compatible with browsers.
 
 ## Learn more