Add the release notes template

ReleaseNotes/release_notes_template.md

+{% set categories = [
+    'Configuration',
+    'Decoding', 'Tracking', 'PV finding', 'Muon', 'Calo', 'RICH', 'Jets',
+    'PID', 'Composites', 'Filters', 'Functors',
+    'Event model', 'Persistency',
+    'MC checking', 'Monitoring', 'Luminosity',
+    'Core', 'Conditions', 'Utilities',
+    'Simulation',  'Tuples', 'Accelerators',
+    'Flavour tagging',
+    'Build',
+    ] -%}
+{% set used_mrs = [] -%}
+{% macro section(labels, mrs=merge_requests, used=used_mrs, indent='', highlight='highlight') -%}
+{% for mr in order_by_label(select_mrs(mrs, labels, used), categories) -%}
+  {% set mr_labels = categories|select("in", mr.labels)|list -%}
+{{indent}}- {% if mr_labels %}{{mr_labels|map('label_ref')|join(' ')}} | {% endif -%}
+    {{mr.title|sentence}}, {{mr|mr_ref(project_fullname)}} (@{{mr.author.username}}){% if mr.issue_refs %} [{{mr.issue_refs|join(',')}}]{% endif %}{% if highlight in mr.labels %} :star:{% endif %}
+{# {{mr.description|mdindent(2)}} -#}
+{% endfor -%}
+{% endmacro -%}
+{{date}} {{project}} {{version}}
+===
+
+This version uses
+{{project_deps[:-1]|join(',\n')}} and
+{{project_deps|last}}.
+
+This version is released on `stripping21-firstpass-patches` branch. It is intended for patches to the pp full stripping (S21r1, S21) in 2011 and 2012 simulation workflows. Builds with gcc48 on slc6
+Built relative to {{project}} [{{project_prev_tag}}](../-/tags/{{project_prev_tag}}), with the following changes:
+
+### New features ~"new feature"
+
+{{ section(['new feature']) }}
+
+### Fixes ~"bug fix" ~workaround
+
+{{ section(['bug fix', 'workaround']) }}
+
+### Enhancements ~enhancement
+
+{{ section(['enhancement']) }}
+
+### Code cleanups and changes to tests ~modernisation ~cleanup ~testing
+
+{{ section(['cleanup', 'modernisation', 'testing']) }}
+
+### Documentation ~Documentation
+
+{# Collect documentation independently, may lead to repeated entries -#}
+{{ section(['Documentation'], used=None) }}
+{# Mark as used such documentation does not appear under Other -#}
+{% set dummy = section(['Documentation']) -%}
+
+### Other
+
+{{ section([[]]) }}