chore: update commitlint config

Updated commitlint config to match Ratkaisutoimisto's new conventions:

* added `deps` as an allowed commit type
* started using JSON config file `.commitlintrc.json` instead of
  Javascript `commitlint.config.js`

.commitlintrc.json

@@ -0,0 +1,39 @@
+{
+  "extends": [
+    "@commitlint/config-conventional"
+  ],
+  "rules": {
+    "header-max-length": [
+      2,
+      "always",
+      72
+    ],
+    "body-max-line-length": [
+      2,
+      "always",
+      72
+    ],
+    "body-leading-blank": [
+      2,
+      "always"
+    ],
+    "type-enum": [
+      2,
+      "always",
+      [
+        "build",
+        "chore",
+        "ci",
+        "deps",
+        "docs",
+        "feat",
+        "fix",
+        "perf",
+        "refactor",
+        "revert",
+        "style",
+        "test"
+      ]
+    ]
+  }
+}