chore: enforce commit message conventions (#1561)

This commit introduces enforcement of commit message policy describe in organization
wide CONTRIBUTING.md file (https://github.com/swagger-api/.github/blob/master/CONTRIBUTING.md).

Along with that, improves discovery of the global CONTRIBUTING.md file by mentioning it
directly in README.md file.

Author: char0n

.commitlintrc.json

@@ -0,0 +1,21 @@
+{
+  "extends": [
+    "@commitlint/config-conventional"
+  ],
+  "rules": {
+    "header-max-length": [2, "always", 69],
+    "scope-case": [
+      2,
+      "always",
+      [
+        "camel-case",
+        "kebab-case",
+        "upper-case"
+      ]
+    ],
+    "subject-case": [
+      0,
+      "always"
+    ]
+  }
+}

.huskyrc

@@ -0,0 +1,5 @@
+{
+  "hooks": {
+    "commit-msg": "commitlint -E HUSKY_GIT_PARAMS"
+  }
+}

README.md

@@ -32,6 +32,7 @@ We'll be consolidating that soon. Just giving you the heads up. You may see refe
 
 #### Development
 
+- [Contributing](https://github.com/swagger-api/.github/blob/master/CONTRIBUTING.md)
 - [Setting up](docs/development/setting-up.md)
 - [Scripts](docs/development/scripts.md)