Separate introduction into project and system

docs/source/introduction.rst

+Introduction
+============
+
+Here we give a short intrduction to both the project as a whole and our system.
+
+.. toctree::
+    :maxdepth: 2
+
+    introduction/project
+    introduction/system

docs/source/introduction/project.md

+# Introduction to the project
+
+Here we give short introduction to the project.
+We also give links to other relevant things to read before choosing this project.

docs/source/introduction.md → docs/source/introduction/system.md

-# Introduction
+# Introduction to our system
 
 This system was allows a user to create, edit and host competitions.