add templated file for reactor configuration and update pillar.example.

salt/files/master.d/reactor.conf

@@ -0,0 +1,15 @@
+#
+# This file is managed by Salt! Do not edit by hand!
+#
+{%- set reactors = salt['pillar.get']('salt:reactor') -%}
+{%- if reactors %}
+reactor:
+{%- for reactor in reactors %}
+{%- for event_tag, reactor_files in reactor.items() %}
+  - '{{ event_tag }}'
+{%- for reactor_file in reactor_files %}
+    - {{ reactor_file }}
+{%- endfor %}
+{%- endfor %}
+{% endfor -%}
+{%- endif -%}