Release 9 8 4 (#749)

* Release 9.8.4

* Update release notes

Author: KazuCocoa

CHANGELOG.md

@@ -3,9 +3,17 @@ Commit based release not is [release_notes.md](./release_notes.md)
 
 Release tags are https://github.com/appium/ruby_lib/releases .
 
+
 ## [Unreleased]
 ### 1. Enhancements
 
+### 2. Bug fixes
+
+### 3. Deprecations
+
+## v9.8.4
+### 1. Enhancements
+
 ### 2. Bug fixes
 - Fix `TypeError: superclass mismatch for class Test` for minitest `5.11.0`+ [PR](https://github.com/appium/ruby_lib/pull/748)