feat: set tag author and committer name/email

Use [Git Environment Variables](https://git-scm.com/book/en/v2/Git-Internals-Environment-Variables#Committing). Set default values if environement variables are not set.

lib/definitions/plugins.js

@@ -1,5 +1,5 @@
 const {isString, isFunction, isArray, isPlainObject} = require('lodash');
-const RELEASE_TYPE = require('./release-types');
+const {RELEASE_TYPE} = require('./constants');
 
 const validatePluginConfig = conf => isString(conf) || isString(conf.path) || isFunction(conf);