feat: configure npm publishing to GitHub Packages registry

- Scope package name to @addono/gh-attach for GitHub Packages compatibility
- Add @semantic-release/npm plugin to .releaserc.json
- Add publishConfig with GitHub Packages registry URL
- Add packages:write permission and NODE_AUTH_TOKEN to release workflow
- Configure registry-url in setup-node step
- Update README install instructions for scoped package

Closes #17

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Addono

.github/workflows/release.yml

@@ -7,6 +7,7 @@ on:
 permissions:
   contents: write
   issues: write
+  packages: write
 
 jobs:
   release:
@@ -20,6 +21,7 @@ jobs:
         with:
           node-version: 22
           cache: npm
+          registry-url: https://npm.pkg.github.com
       - run: npm ci
       - run: npm run build
       - run: npm test
@@ -28,3 +30,5 @@ jobs:
         run: npx semantic-release
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          NODE_AUTH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          NPM_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.releaserc.json

@@ -9,6 +9,7 @@
         "changelogFile": "CHANGELOG.md"
       }
     ],
+    "@semantic-release/npm",
     [
       "@semantic-release/github",
       {

README.md

@@ -22,8 +22,8 @@ GitHub doesn't provide an official API for attaching images to issues and pull r
 ## Install
 
 ```bash
-# npm (standalone)
-npm install -g gh-attach
+# npm (standalone, from GitHub Packages)
+npm install -g @addono/gh-attach --registry=https://npm.pkg.github.com
 
 # gh extension
 gh extension install Addono/gh-attach

package.json

@@ -1,5 +1,5 @@
 {
-  "name": "gh-attach",
+  "name": "@addono/gh-attach",
   "version": "0.0.0-development",
   "description": "CLI tool and MCP server for attaching images to GitHub issues, PRs, and comments",
   "type": "module",
@@ -68,6 +68,9 @@
     "type": "git",
     "url": "https://github.com/Addono/gh-attach.git"
   },
+  "publishConfig": {
+    "registry": "https://npm.pkg.github.com"
+  },
   "engines": {
     "node": ">=20"
   },