Update CHANGELOG for v3.4.9

Author: andyleejordan

CHANGELOG.md

@@ -1,5 +1,14 @@
 # PowerShell Editor Services Release History
 
+## v3.4.9
+### Thursday, August 11, 2022
+
+- ✨ 🚨 [PowerShellEditorServices #1874](https://github.com/PowerShell/PowerShellEditorServices/pull/1874) - Add end-to-end integration test with Vim.
+- 🐛 ‍🕵️ [vscode-powershell #4112](https://github.com/PowerShell/PowerShellEditorServices/pull/1873) - Fix (and test) regression with PSScriptAnalyzer default rules.
+- ✨ 🚨 [PowerShellEditorServices #1872](https://github.com/PowerShell/PowerShellEditorServices/pull/1872) - Add regression tests for parse error DiagnosticMarkers. (Thanks @fflaten!)
+- ✨ 🚨 [PowerShellEditorServices #1870](https://github.com/PowerShell/PowerShellEditorServices/pull/1870) - Add `DoesNotDuplicateScriptMarkersAsync` regression test.
+- 🐛 ‍🕵️ [PowerShellEditorServices #1869](https://github.com/PowerShell/PowerShellEditorServices/pull/1869) - Fix duplicate DiagnosticMarkers when reopening a file. (Thanks @fflaten!)
+
 ## v3.4.8
 ### Wednesday, August 03, 2022