Bump mynahui to 4.21.5 and update /help output (#5275)

- Bumped MynahUI to version 4.21.5 from 4.21.2. This includes four bug fixes and one feature, as described by the changelog additions and by the [MynahUI release notes](https://github.com/aws/mynah-ui/releases).

- Updated the `/help` command output to include the new re:invent 2024 features. Copied from the [VSCode toolkit repo's constant](https://github.com/aws/aws-toolkit-jetbrains/blob/770f2a27e0c8f59dd4229b67e3a861a590a0d33d/plugins/amazonq/chat/jetbrains-community/src/software/aws/toolkits/jetbrains/services/cwc/controller/chat/StaticTextResponse.kt#L31).

Author: Jurredr

.changes/next-release/bugfix-16ca3d82-920e-4b67-9cba-a43e4fcc35a6.json

@@ -0,0 +1,4 @@
+{
+  "type" : "bugfix",
+  "description" : "Amazon Q: Fix context menu displaying when typing `@`, even though input is disallowed"
+}

.changes/next-release/bugfix-4eafd62e-c6c7-4d59-b7cd-d96ee217eaff.json

@@ -0,0 +1,4 @@
+{
+  "type" : "bugfix",
+  "description" : "Amazon Q: Fix up/down history navigation only triggering on first/last line of prompt input"
+}

.changes/next-release/bugfix-a017d3fa-ff27-418d-b835-169a8c72c021.json

@@ -0,0 +1,4 @@
+{
+  "type" : "bugfix",
+  "description" : "Amazon Q: cursor no longer jumps after navigating prompt history"
+}

.changes/next-release/bugfix-f612e704-cb5b-4eb5-b67d-bd0f5d28bae6.json

@@ -0,0 +1,4 @@
+{
+  "type" : "bugfix",
+  "description" : "Amazon Q: word duplication when pressing tab on context selector fixed"
+}

.changes/next-release/feature-982d469e-e6b7-456b-9f63-211c4193e8a9.json

@@ -0,0 +1,4 @@
+{
+  "type" : "feature",
+  "description" : "Amazon Q: Updated `/help` command to include re:invent 2024 features"
+}

.changes/next-release/feature-d9e8c826-dd22-4be8-a065-11593b375a7c.json

@@ -0,0 +1,4 @@
+{
+  "type" : "feature",
+  "description" : "Amazon Q: UI improvements through more accurate code syntax highlighting"
+}

plugins/amazonq/chat/jetbrains-community/src/software/aws/toolkits/jetbrains/services/cwc/controller/chat/StaticTextResponse.kt

@@ -28,10 +28,13 @@ enum class StaticTextResponse(
             - Explain the <selected code> and ask clarifying questions about it.
             - What is the syntax of declaring a variable in TypeScript?
             ### Special Commands
-            - /clear - Clear the conversation.
             - /dev - Get code suggestions across files in your current project. Provide a brief prompt, such as "Implement a GET API."
+            - /doc - Create and update documentation for your repository.
+            - /review - Discover and address security and code quality issues.
+            - /test - Generate unit tests for a file.
             - /transform - Transform your code. Use to upgrade Java code versions.
             - /help - View chat topics and commands.
+            - /clear - Clear the conversation.
             ### Things to note:
             - I may not always provide completely accurate or current information.
             - Provide feedback by choosing the like or dislike buttons that appear below answers.

plugins/amazonq/mynah-ui/package-lock.json

@@ -12,7 +12,7 @@
         "lintfix": "eslint -c .eslintrc.js --fix --ext .ts ."
     },
     "dependencies": {
-        "@aws/mynah-ui-chat": "npm:@aws/[email protected].2",
+        "@aws/mynah-ui-chat": "npm:@aws/[email protected].5",
         "@types/node": "^14.18.5",
         "fs-extra": "^10.0.1",
         "sanitize-html": "^2.12.1",