fix: turn on commitlint

Because releases are automated with semantic-release, we need
conventional commits.

.commitlintrc.json

@@ -0,0 +1,12 @@
+{
+  "rules": {
+    "header-max-length": [2, "always", 72],
+    "body-leading-blank": [2, "always"],
+    "type-empty": [2, "never"],
+    "type-enum": [
+      2,
+      "always",
+      ["feat", "fix", "docs", "chore", "refactor", "test", "revert"]
+    ]
+  }
+}

package.json

@@ -19,12 +19,14 @@
     "changelog": "yarn ts-node src/changelog.ts",
     "lint": "run-p lint:*",
     "lint:formatting": "prettier --check 'src/**/*.{js,ts}'",
+    "lint:commits": "commitlint --from=HEAD~1",
     "format": "prettier --write 'src/**/*.{js,ts}'"
   },
   "devDependencies": {
     "@babel/plugin-transform-runtime": "^7.16.0",
     "@babel/preset-env": "^7.16.0",
     "@babel/preset-typescript": "^7.16.0",
+    "@commitlint/cli": "16.0.2",
     "@types/fs-extra": "^9.0.13",
     "@types/jest": "^26.0.24",
     "@types/json-stable-stringify": "^1.0.33",