Update README.md

Author: oprypin

README.md

@@ -11,12 +11,21 @@ Works on Ubuntu, macOS, Windows.
 steps:
   - uses: oprypin/install-crystal@v1
   - run: crystal eval "puts 1337"
+```
+
+```yaml
+steps:
   - uses: actions/checkout@v2
+  - uses: oprypin/install-crystal@v1
+    with:
+      crystal: 0.34.0
   - run: crystal spec
 ```
 
 Also see [.github/workflows/release.yml](.github/workflows/release.yml) as an example.
 
+Alternatively you can use the container-based approach [as in the starter workflow][crystal-starter] (without this action), but the advantage here is the unified approach to installation across 3 systems.
+
 ## Usage
 
 ### Inputs
@@ -55,3 +64,4 @@ Also see [.github/workflows/release.yml](.github/workflows/release.yml) as an ex
 [github action]: https://github.com/features/actions
 [crystal]: https://crystal-lang.org/
 [crystal.git]: https://github.com/crystal-lang/crystal
+[crystal-starter]: https://github.com/actions/starter-workflows/blob/master/ci/crystal.yml