Add snapcraft packaging information (#6084)

.gitignore

@@ -7,6 +7,7 @@
 *.egg-info
 *.lock
 *.pyc
+*.snap
 *.tac
 _trial_temp/
 _trial_temp*/

changelog.d/6084.misc

+Add snapcraft packaging information. Contributed by @devec0.

snap/snapcraft.yaml

+name: matrix-synapse
+base: core18
+version: git 
+summary: Reference Matrix homeserver
+description: |
+  Synapse is the reference Matrix homeserver.
+  Matrix is a federated and decentralised instant messaging and VoIP system.
+
+grade: stable 
+confinement: strict 
+
+apps:
+  matrix-synapse: 
+    command: synctl --no-daemonize start $SNAP_COMMON/homeserver.yaml
+    stop-command: synctl -c $SNAP_COMMON stop
+    plugs: [network-bind, network]
+    daemon: simple 
+parts:
+  matrix-synapse:
+    source: .
+    plugin: python
+    python-version: python3