wip: adds README

Author: jmgilman

forge/actions/discovery/README.md

@@ -1,3 +1,45 @@
 # Discover Action
 
-TODO
+The discover action acts as a wrapper over the `forge scan` command from the Forge CLI.
+It provides inputs that map to their respective flags.
+The result from running the command is returned in the `result` output.
+By default, the `--enumerate` flag is passed as this is usually the desired output format in CI.
+
+For more information on the `scan` command, refer to the Forge CLI documentation.
+
+## Usage
+
+```yaml
+name: Run Setup
+on:
+  push:
+
+permissions:
+  contents: read
+  id-token: write
+
+jobs:
+  setup:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Setup
+        uses: input-output-hk/catalyst-forge/forge/actions/setup@master
+      - name: Discover
+        id: discovery
+        uses: input-output-hk/catalyst-forge/forge/actions/discover@master
+        with:
+          filters: |
+            ^check.*
+            ^test.*
+      - name: Show result
+        run: echo "${{ steps.discovery.outputs.result }}
+```
+
+## Inputs
+
+| Name      | Description                                   | Required | Default   |
+| --------- | --------------------------------------------- | -------- | --------- |
+| absolute  | Output absolute paths                         | No       | `"false"` |
+| enumerate | Enumerate results into Earthfile+Target pairs | No       | `"true"`  |
+| filters   | A newline separated list of filters to apply  | No       | `""`      |
+| path      | The path to search from                       | No       | `"."`     |