add autocapitalize info stenciljs/core#3692

Author: rwaskiewicz

src/docs/introduction/upgrading-to-stencil-three.md

@@ -87,6 +87,11 @@ Please upgrade local development machines, continuous integration pipelines, etc
 ```
 `event` arguments to either callback should be updated to take this narrower typing into account
 
+### Narrowed Typing for `autocapitalize` Attribute
+The [`autocaptialize` attribute](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/autocapitalize) has been narrowed from type `any` to type `string`.
+This changes brings Stencil into closer alignment with TypeScript's typings for the attribute.
+No explicit changes are needed, unless a project was passing non-strings to the attribute.
+
 ## Output Targets
 
 ### `dist-custom-elements` Output Target