Create pleroma.email mix task

Closes: https://git.pleroma.social/pleroma/pleroma/issues/1061

docs/administration/CLI_tasks/email.md

@@ -0,0 +1,24 @@
+# Managing emails
+
+{! backend/administration/CLI_tasks/general_cli_task_info.include !}
+
+## Send test email (instance email by default)
+
+```sh tab="OTP"
+ ./bin/pleroma_ctl email test [--to <destination email address>]
+```
+
+```sh tab="From Source"
+mix pleroma.email test [--to <destination email address>]
+```
+
+
+Example: 
+
+```sh tab="OTP"
+./bin/pleroma_ctl email test --to root@example.org
+```
+
+```sh tab="From Source"
+mix pleroma.email test --to root@example.org
+```