Prepare CHANGELOG.md for M86 (#8262)

https://github.com/flutter/flutter-intellij/milestone/98

Author: jwren

CHANGELOG.md

@@ -1,3 +1,10 @@
+# 86
+- New message in DevTools windows for "Dock unpinned" IntelliJ feature (#8181)
+- Fixes for Slow Operation notifications in the IDEA platform (#7792)
+- Fix in Flutter project creation flow (#8259)
+- Many code health improvements and code cleanups (#8025, #8027, #8021)
+- Migration of deprecated API usages (#7718)
+
 # 85.3
 - Add Property Editor side panel (#7957)
 - Support removed for IDEA 2024.1 (Koala) and 2024.2 (Ladybug) (#8073)

resources/META-INF/plugin.xml

@@ -50,6 +50,14 @@
 
   <change-notes>
     <![CDATA[
+<h1>86</h1>
+<ul>
+  <li>New message in DevTools windows for &quot;Dock unpinned&quot; IntelliJ feature (#8181)</li>
+  <li>Fixes for Slow Operation notifications in the IDEA platform (#7792)</li>
+  <li>Fix in Flutter project creation flow (#8259)</li>
+  <li>Many code health improvements and code cleanups (#8025, #8027, #8021)</li>
+  <li>Migration of deprecated API usages (#7718)</li>
+</ul>
 <h1>85.3</h1>
 <ul>
   <li>Add Property Editor side panel (#7957)</li>