chore: update release notes template (#69)

Fixes #65

Author: afuetterer

.github/templates/.release_notes.md.j2

@@ -1,6 +1,10 @@
 {%- set releases = context.history.released.items() | list -%}
 {%- set prev_version = releases[1][0] -%}
 ## Release Notes
-
 {% include ".changes.j2" %}
 {{ "**Full Changelog**: (%s)" | format(prev_version | compare_url(version)) }}
+## Installation
+You can install this version via pip from [PyPI](https://pypi.org/project/python-re3data/{{ version }}/):
+```console
+python -m pip install python-re3data=={{ version }}
+```