docs: mention problem matcher

Author: nekowinston

README.md

@@ -4,8 +4,13 @@
 
 ### Deno Setup action with integrated cache.
 
-Based on `denoland/setup-deno@v1`, & `actions/cache@v3`, handles `DENO_DIR` and caching for you.\
-Works on Ubuntu, macOS & Windows runners.
+- Based on: 
+  - [`denoland/setup-deno@v1`](https://github.com/denoland/setup-deno),
+  - [`actions/cache@v3`](https://github.com/actions/cache)
+- Handles restoring and caching to `DENO_DIR` for you.
+- Annotates your source code from `deno lint --compact` output.\
+  See the summary of the most recent [Problem Matcher worflow](https://github.com/nekowinston/setup-deno/actions/workflows/problem-matcher.yml) for an example.
+- Works on Ubuntu, macOS & Windows runners.
 
 ### Usage