adding tools page

Author: mtf90

_data/navigation.yml

@@ -11,4 +11,6 @@
 - title: Resources
   items:
     - title: Version History
-      url: /pages/version-history
+      url: /pages/version-history
+    - title: Tools using LearnLib
+      url: /pages/tools

pages/tools.md

@@ -0,0 +1,16 @@
+---
+layout: default
+title: "Tools using Learning"
+navbar-group: "Resources"
+---
+
+## Tools using LearLib
+
+This page lists (external) tools that are connected to LearnLib or its related projects either by using them as is or extending them with new features.
+The goal of this page is to provide an overview of the LearnLib community and share information for fruitful collaborations in the future.
+
+## Tools
+
+The following projects are listed in alphabetical order.
+
+* **Coal** (COmpositional Automata Learner, [link](https://doi.org/10.1007/978-3-031-30826-0_3), [link](https://zenodo.org/records/7777664)) is a tool for learning compositional systems that allows for *unknown* membership query results. Hypotheses are constructed via passive learning techniques or SAT solving.