Issue #3358942: Add a composer.json file

composer.json

+{
+  "name": "drupal/forum",
+  "type": "drupal-module",
+  "license": "GPL-2.0-or-later",
+  "description": "This module provides discussion forums.",
+  "homepage": "https://www.drupal.org/project/forum",
+  "authors": [
+    {
+      "name": "Lee Rowlands",
+      "homepage": "https://www.drupal.org/u/larowlan",
+      "role": "Maintainer"
+    },
+    {
+      "name": "Andrey Postnikov",
+      "homepage": "https://www.drupal.org/u/andypost",
+      "role": "Maintainer"
+    },
+    {
+      "name": "Peter Majmesku",
+      "homepage": "https://www.drupal.org/u/peter-majmesku",
+      "role": "Maintainer"
+    }
+  ],
+  "support": {
+    "issues": "https://www.drupal.org/project/issues/forum",
+    "source": "https://git.drupalcode.org/project/forum"
+  },
+  "require": {}
+}