update docs

README.md

@@ -1,6 +1,29 @@
 # uv-cache
 
 This is a very simple action that sets up cache support for `uv`. It doesn't do
-anything else. It's assumed that `uv`, as well as all the dependencies for
-`actions/cache@v4` are available in the container. I wrote this to work well
-with [based-alpine](https://git.ficd.sh/ficd/based-alpine).
+anything else. I wrote this to work well with
+[based-alpine](https://git.ficd.sh/ficd/based-alpine).
+
+## Requirements
+
+All dependencies `actions/cache@v4` must be satisfied, and `uv` must be
+available on the path.
+
+## Usage
+
+Using this action is very simple. We also provide one output: `cache-hit`, which
+is either "true" or "false".
+
+```yaml
+# you should always checkout first
+# otherwise there is nothing to check cache against
+- name: checkout source
+  uses: actions/checkout@v4
+- name: setup cache
+  # assign the id if you want to check the boolean later
+  id: uv-cache
+  uses: https://git.ficd.sh/ficd/uv-cache@v1
+- name: Check cache status
+  run: |
+    echo "Cache hit? ${{ steps.uv-cache.outputs.cache-hit }}"
+```