build(package): downgrade standard-version@6

Because standard-version >=6 no longer bumps package with 0.x.x
version correctly.

Author: remarkablemark

package.json

@@ -58,7 +58,7 @@
     "rollup-plugin-commonjs": "^10.1.0",
     "rollup-plugin-node-resolve": "^5.2.0",
     "rollup-plugin-uglify": "^6.0.4",
-    "standard-version": "^6",
+    "standard-version": "^5",
     "typescript": "^3.9.3"
   },
   "peerDependencies": {