Update instructions

Author: oprypin

README.md

@@ -1,12 +1,10 @@
 install-crystal
 ===============
 
-[GitHub Action][] to **install [Crystal][] programming language**
+[GitHub Action][] to **install [Crystal][] programming language** and [Shards][] package manager.
 
 Works on Ubuntu, macOS, Windows.
 
-On Ubuntu and macOS this also installs `shards`. This will be expanded in the future.
-
 ## Examples
 
 ```yaml
@@ -20,10 +18,20 @@ steps:
   - uses: actions/checkout@v2
   - uses: oprypin/install-crystal@v1
     with:
-      crystal: 0.34.0
+      crystal: 0.35.0
   - run: crystal spec
 ```
 
+```yaml
+steps:
+  - uses: actions/checkout@v2
+  - uses: oprypin/install-crystal@v1
+    with:
+      shards: true
+  - run: shards install
+```
+
+
 [Find usages in the wild!](https://github.com/search?l=YAML&q=%22oprypin%2Finstall-crystal%22&type=Code)
 
 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.
@@ -32,17 +40,38 @@ Alternatively, you can use the container-based approach [as in the starter workf
 
 ### Inputs
 
-* **`crystal: 0.34.0`** (not supported on Windows)
+* * **`crystal: 0.35.0`** (not supported on Windows)
+
+    Install a particular release of Crystal.
+
+  * **`crystal: latest`** (default; not supported on Windows)
+
+    Install the latest released version of Crystal.
+
+  * **`crystal: nightly`** (default on Windows)
+
+    Install Crystal from the latest continuous build on [crystal.git][] master.
+
+* * **`shards: true`** (default)
+
+    Ensure that *some* released version of [Shards][] is available (or `nightly` on Windows).  
+    This uses the build that's bundled with Crystal's releases. Other options are slower, as building Shards is a necessary step then.
+    
+  * **`shards: false`** (default on Windows)
+    
+    Ensure that `shards` executable is *not* available.
+
+  * **`shards: latest`** (not supported on Windows)
 
-  Install a particular release of Crystal.
+    Build and install the latest released version of Shards.
 
-* **`crystal: latest`** (default; not supported on Windows)
+  * **`shards: 0.12.0`** (not supported on Windows)
 
-  Install the latest released version of Crystal.
+    Build and install a particular release of Shards.
 
-* **`crystal: nightly`** (default on Windows)
+  * **`shards: nightly`**
 
-  Install Crystal from the latest continuous build on [crystal.git][] master.
+    Build and install the latest commit of [shards.git][] master.
 
 * **`arch: x86_64`**, **`arch: x86`** (defaults to current OS arch)
 
@@ -66,4 +95,6 @@ Alternatively, you can use the container-based approach [as in the starter workf
 [github action]: https://github.com/features/actions
 [crystal]: https://crystal-lang.org/
 [crystal.git]: https://github.com/crystal-lang/crystal
+[shards]: https://github.com/crystal-lang/shards
+[shards.git]: https://github.com/crystal-lang/shards
 [crystal-starter]: https://github.com/actions/starter-workflows/blob/master/ci/crystal.yml