chore(docs): update BREAKING_CHANGES.md for assetsDir backwards com…

…pat (#3343)

In #3341 we removed backwards compatibility for the deprecated
`assetsDir` component decorator prop. This updates the BREAKING_CHANGES
document to reflect that change.

STENCIL-410: Remove Backwards Compatibility for assetDir Field on @component

BREAKING_CHANGES.md

@@ -651,4 +651,21 @@ When running Jest directly, previously most of Jest had to be manually configure
 Stencil v3.0.0 is in development at this time and has not been released. The list below is not final and is subject to
 change. Further details on each of these items will be included prior to the release.
 
-- [fix(testing): puppeteer v10 support #2934](https://github.com/ionic-team/stencil/pull/2934)
+- [fix(testing): puppeteer v10 support #2934](https://github.com/ionic-team/stencil/pull/2934)
+
+## DEPRECATIONS
+
+### backwards compatibility for `@Component.assetsDir` EOL
+
+The `assetsDir` component prop was [previously deprecated](#componentassetsdir)
+but some backwards compatibility was retained with a warning message. In
+Stencil V3 this backwards compatibility is being removed and Stencil users will
+have to remove all usage of `assetsDir` in favor of `assetsDirs`.
+
+
+```diff
+@Component({
+-  assetsDir: 'resource',
++  assetsDirs: ['resource']
+})
+```