feat: ensure spud correctly installed and placed on PATH

Reviewed-on: #1
Co-authored-by: Marc Cataford <mcat@riseup.net>
Co-committed-by: Marc Cataford <mcat@riseup.net>

README.md

@@ -0,0 +1,11 @@
+# Setup Spud Action
+
+## Interface
+
+```yaml
+inputs:
+  version:
+    description: "Spud version to install."
+```
+
+If the `version` input is not provided, the latest version will be installed (see [spadinastan/spud](https://forge.karnov.club/spadinastan/spud)).

action.yml

@@ -1,10 +1,14 @@
-name: Setup Spud
+name: Setup Spud Tooling
 inputs:
   version:
     description: "Spud version to install."
 runs:
   using: composite
   steps:
+    - name: Ensure install directory exists and is on PATH
+      run: |
+        mkdir -p $HOME/.local/bin
+        echo "$HOME/.local/bin" >> $GITHUB_PATH
     - name: Pull pre-built binary
       env:
         SPUD_VERSION: ${{ inputs.version }}