docs: add changelog to documentation

CHANGELOG.md

-# Changelog
-
-## v0.1.2
+v0.1.2
+------
 
 * Elaborate on installation. Use pip from conda-forge channel to install `PSimPy`
 
 * Add info about how tests can be run
 
-## v0.1.1
+v0.1.1
+------
 
 * Add info about installation
 
@@ -14,6 +14,7 @@
 
 * Update metadata
 
-## v0.1.0
+v0.1.0
+------
 
 * First release

docs/source/changelog.rst

-```{include} ../CHANGELOG.md
-```
\ No newline at end of file
+Changes
+=======
+
+.. include:: ../../CHANGELOG.md