feat: add success and fail notification plugins

- Allow `publish` plugins to return an `Object` with information related to the releases
- Add the `success` plugin hook, called when all `publish` are successful, receiving a list of release
- Add the `fail` plugin hook, called when an error happens at any point, receiving a list of errors
- Add detailed message for each error

lib/get-error.js

@@ -0,0 +1,7 @@
+const SemanticReleaseError = require('@semantic-release/error');
+const ERROR_DEFINITIONS = require('./definitions/errors');
+
+module.exports = (code, ctx = {}) => {
+  const {message, details} = ERROR_DEFINITIONS[code](ctx);
+  return new SemanticReleaseError(message, code, details);
+};