Add list of TUF implementations

implementations.md

@@ -0,0 +1,44 @@
+# TUF implementations
+
+We list open source implementations of TUF in several languages, along with links to project code and documentation. This list is not an endorsement of any project, but rather a resource for interested users and contributors. It excludes the various closed-source implementations of the project. If there is an implementation or piece of documentation missing from this list, please open a pr on this repository to update it.
+
+## python-tuf
+
+* [source code](https://github.com/theupdateframework/python-tuf)
+
+## go-tuf
+
+* [source code](https://github.com/theupdateframework/go-tuf)
+
+## rust-tuf
+
+* [source code](https://github.com/theupdateframework/rust-tuf)
+
+## tough
+
+* [source code](https://github.com/awslabs/tough)
+
+## php-tuf
+
+* [source code](https://github.com/php-tuf/php-tuf)
+
+## tuf-js
+
+* [source code](https://github.com/theupdateframework/tuf-js)
+
+## Notary
+
+* [source code](https://github.com/notaryproject/notary)
+
+## Variants of TUF
+
+These implementations implement a variation of the TUF specification
+
+### Aktualizer
+
+* [source code](https://github.com/uptane/aktualizr)
+* An implementation of the TUF variant [Uptane](https://uptane.github.io/)
+
+### The Archive Framework (TAF)
+
+* [source code](https://github.com/openlawlibrary/taf)