docs: add missing TOC to Migration Guide (#647)

SuzukiKatsuma · web-flow · commit 9918cb6487eb · 2024-07-08T22:05:12.000+02:00
diff --git a/docs/migration-guide.md b/docs/migration-guide.md
@@ -9,6 +9,7 @@
   - [Executing some function before preprocessing](#executing-some-function-before-preprocessing)
   - [Defining preprocessor properties](#defining-preprocessor-properties)
   - [Type-checking components](#type-checking-components)
+- [From `v5` to `v6`](#from-v5-to-v6)
 
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