Merge ~hloeung/smtp-dkim-signing-charm:master into smtp-dkim-signing-charm:master

[Haw Loeung]

Add lint and unit tests to each commit with lpcraft

This can be run locally with `lpcraft run` (after installing the lpcraft snap), or will now be run on every commit, and output will be shown in merge proposals as below.

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

This merge proposal is being monitored by mergebot. Change the status to Approved to merge.

[Junien F (axino)]

review: Approve

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

Change successfully merged at revision 1c61fd625a0d96be90b5498dc5b58792896f6917

diff --git a/.launchpad.yaml b/.launchpad.yaml
 new file mode 100644
index 0000000..2c63e5a
--- /dev/null
+++ b/.launchpad.yaml
@@ -0,0 +1,19 @@
+pipeline:
+  - lint
+  - unittest
+
+jobs:
+  lint:
+    architectures: amd64
+    series: focal
+    packages:
+      - tox
+    run: |
+      tox -e lint
+  unittest:
+    architectures: amd64
+    series: focal
+    packages:
+      - tox
+    run: |
+      tox -e unit