Add an initial changelog to the Dart IntelliJ plugin (#40)

This resolves #23

Author: jwren

third_party/CHANGELOG.md

@@ -0,0 +1,14 @@
+# Dart Plugin for IntelliJ Changelog
+
+## [Unreleased]
+
+ - Vendor change from "JetBrains" to "Google"
+ - Build system change from Basel to Gradle
+ - Removal of the old Code Coverage support, all references to com.intellij.coverage.*
+ - New Dart language feature: Dot Shorthands (https://youtrack.jetbrains.com/issue/IDEA-370100)
+ - Support new 'Null-Aware Elements’ syntax (https://youtrack.jetbrains.com/issue/IDEA-374053)
+ - Fix: IDE freezes after inserting a piece of Dart code (https://youtrack.jetbrains.com/issue/IDEA-231468)
+ - Fix: DartParser performance issue: sluggish typing in the editor (https://youtrack.jetbrains.com/issue/IDEA-365957)
+ - Fix: Format of very long line gives uncompilable code (https://youtrack.jetbrains.com/issue/IDEA-328345)
+ - Fix: Cannot save Dart line length in Settings (https://youtrack.jetbrains.com/issue/IDEA-322573)
+ - Closing labels should look like inlay hints, not like real comments (https://youtrack.jetbrains.com/issue/IDEA-289260)

third_party/build.gradle.kts

@@ -34,12 +34,13 @@ intellijPlatform {
         name = providers.gradleProperty("pluginName")
         id = providers.gradleProperty("pluginId")
         version = providers.gradleProperty("pluginVersion")
-        // TODO(https://github.com/flutter/dart-intellij-third-party/issues/23) Add a changelog:
-        // val changelog = ...
         ideaVersion {
             sinceBuild = providers.gradleProperty("pluginSinceBuild")
             untilBuild = providers.gradleProperty("pluginUntilBuild")
         }
+        changeNotes = provider {
+            file("CHANGELOG.md").readText(Charsets.UTF_8)
+        }
     }
     pluginVerification {
         failureLevel = listOf(