[Tests] add nyc for coverage

.nycrc

@@ -0,0 +1,13 @@
+{
+	"all": true,
+	"check-coverage": false,
+	"reporter": ["text-summary", "text", "html", "json"],
+	"lines": 86,
+	"statements": 85.93,
+	"functions": 82.43,
+	"branches": 76.06,
+	"exclude": [
+		"coverage",
+		"test"
+	]
+}

package.json

@@ -15,7 +15,7 @@
 		"prepublish": "not-in-publish || npm run prepublishOnly",
 		"prepublishOnly": "safe-publish-latest",
 		"pretest": "npm run lint",
-		"tests-only": "tape test",
+		"tests-only": "nyc tape test",
 		"test": "npm run tests-only",
 		"posttest": "aud --production"
 	},
@@ -55,6 +55,7 @@
 		"for-each": "^0.3.3",
 		"in-publish": "^2.0.1",
 		"npmignore": "^0.3.0",
+		"nyc": "^10.3.2",
 		"object-inspect": "^1.12.2",
 		"safe-publish-latest": "^2.0.0",
 		"tape": "^5.6.1"