Update CHANGELOG for v3.0.3

Author: andyleejordan

CHANGELOG.md

@@ -1,5 +1,14 @@
 # PowerShell Editor Services Release History
 
+## v3.0.3
+### Monday, December 20, 2021
+
+- 🐛 🚂 [vscode-powershell #3718](https://github.com/PowerShell/PowerShellEditorServices/pull/1647) - Create `$psEditor` as a constant.
+- #️⃣ 🙏 [PowerShellEditorServices #1641](https://github.com/PowerShell/PowerShellEditorServices/pull/1641) - Added check to see if `PSModulePath` already contained `BundledModulePath`. (Thanks @dkattan!)
+- #️⃣ 🙏 [PowerShellEditorServices #1640](https://github.com/PowerShell/PowerShellEditorServices/pull/1640) - Implemented `-LanguageServiceOnly` switch. (Thanks @dkattan!)
+- 🐛 🛫 [PowerShellEditorServices #1638](https://github.com/PowerShell/PowerShellEditorServices/pull/1638) - Fix `BundledModulePath` and PSReadLine loading (redux).
+- 🐛 🔍 [PowerShellEditorServices #1635](https://github.com/PowerShell/PowerShellEditorServices/pull/1635) - Re-enable `DebugServiceTests` suite.
+
 ## v3.0.2
 ### Monday, November 22, 2021