feat: add curl|sh one-liner install script

- Add scripts/install.sh for easy installation via curl
- Auto-detects OS (linux, darwin, windows) and arch (amd64, arm64)
- Supports version pinning: sh -s -- v1.2.3
- Installs to /usr/local/bin or ~/.local/bin as fallback
- Updates release workflow to include install.sh in release assets
- Adds README.md with installation documentation

.github/workflows/release.yml

@@ -109,6 +109,11 @@ jobs:
           find . -type f \( -name "*.tar.gz" -o -name "*.zip" \) -exec sha256sum {} \; > ../checksums.txt
           cat ../checksums.txt
 
+      - name: Get install script
+        run: |
+          cp scripts/install.sh install.sh
+          chmod +x install.sh
+
       - name: Create Release
         uses: softprops/action-gh-release@v1
         with:
@@ -127,16 +132,18 @@ jobs:
             
             ### Installation
             
-            **Linux/macOS:**
+            **One-liner (Linux/macOS):**
             ```bash
-            # Download and extract
-            curl -sL https://github.com/openboatmobile/obm/releases/download/${{ steps.version.outputs.VERSION }}/obm-$(uname -s | tr '[:upper:]' '[:lower:]')-$(uname -m | sed 's/x86_64/amd64/').tar.gz | tar xz
-            chmod +x obm
-            sudo mv obm /usr/local/bin/
+            curl -fsSL https://raw.githubusercontent.com/openboatmobile/obm/main/scripts/install.sh | sh
             ```
             
-            **Windows:**
-            Download the appropriate `.zip` file, extract, and add to PATH.
+            Or install a specific version:
+            ```bash
+            curl -fsSL https://raw.githubusercontent.com/openboatmobile/obm/main/scripts/install.sh | sh -s -- v1.2.3
+            ```
+            
+            **Manual download:**
+            Download the archive for your platform, extract, and place `obm` in your PATH.
             
             ### Usage
             ```bash
@@ -149,6 +156,7 @@ jobs:
             artifacts/**/obm-*.tar.gz
             artifacts/**/obm-*.zip
             checksums.txt
+            install.sh
           draft: false
           prerelease: ${{ contains(steps.version.outputs.VERSION, '-') }}
           generate_release_notes: false