Add poste.io (#84)

* add poste.io

* fix docs in poste.io; use proper docker image tag

public/v1/apps/poste-io.json

@@ -0,0 +1,55 @@
+{
+  "captainVersion": "1",
+  "documentation": "Read the poste.io documentation @ https://poste.io/doc",
+  "dockerCompose": {
+    "version": "3.7",
+    "services": {
+      "$$cap_appname": {
+        "image": "analogic/poste.io:$$cap_poste_version",
+        "ports": [
+          "25:25",
+          "110:110",
+          "143:143",
+          "465:465",
+          "587:587",
+          "993:993",
+          "995:995",
+          "4190:4190"
+        ],
+        "volumes": [
+          "/etc/localtime:/etc/localtime:ro",
+          "$$cap_appname-data:/data"
+        ],
+        "restart": "always",
+        "environment": {
+          "HTTPS": "OFF",
+          "LETSENCRYPT_EMAIL": "$$cap_email",
+          "LETSENCRYPT_HOST": "$$cap_host",
+          "VIRTUAL_HOST": "$$cap_host"
+        }
+      }
+    }
+  },
+  "instructions": {
+    "start": "SMTP + IMAP + POP3 + Antispam + Antivirus\nWeb administration + Web email\n...on your server in ~5 minutes\n\nRecommended: Use\"mail\" as the App Name.",
+    "end": "Poste is deployed and available as $$cap_appname. \n\n IMPORTANT: It will take up to 2 minutes for Poste to be ready. Before that, you might see 502 error page.\n"
+  },
+  "variables": [
+    {
+        "id": "$$cap_poste_version",
+        "label": "Poste.io version tag",
+        "description": "Checkout their docker page for the valid tags https://hub.docker.com/r/analogic/poste.io/tags",
+        "defaultValue": "2"
+    },
+    {
+      "id": "$$cap_email",
+      "label": "Email Address",
+      "description": "The email address used for Lets Encrpt certificates."
+    },
+    {
+      "id": "$$cap_host",
+      "label": "Hostname",
+      "description": "The full hostname for this captain app. (usually mail.mydomain.com)"
+    }
+  ]
+}