ci: add semantic-release config, regenerate build icons, normalize Node 20

- Create .releaserc.json with conventional commits, changelog, npm version bump, and GitHub release
- Regenerate all build icons (PNG, ICO, ICNS) from new GN logo
- Normalize Node.js version to 20 across all CI workflows (testing, lint, format, release)

.releaserc.json

@@ -0,0 +1,48 @@
+{
+  "branches": ["main"],
+  "plugins": [
+    ["@semantic-release/commit-analyzer", {
+      "preset": "conventionalcommits",
+      "releaseRules": [
+        { "type": "feat", "release": "minor" },
+        { "type": "fix", "release": "patch" },
+        { "type": "perf", "release": "patch" },
+        { "type": "refactor", "release": "patch" },
+        { "type": "docs", "release": false },
+        { "type": "style", "release": false },
+        { "type": "chore", "release": false },
+        { "type": "ci", "release": false },
+        { "type": "test", "release": false },
+        { "breaking": true, "release": "major" }
+      ]
+    }],
+    ["@semantic-release/release-notes-generator", {
+      "preset": "conventionalcommits",
+      "presetConfig": {
+        "types": [
+          { "type": "feat", "section": "🚀 Features" },
+          { "type": "fix", "section": "🐛 Bug Fixes" },
+          { "type": "perf", "section": "⚡ Performance" },
+          { "type": "refactor", "section": "♻️ Refactors" },
+          { "type": "docs", "section": "📚 Documentation", "hidden": true },
+          { "type": "chore", "section": "🧰 Maintenance", "hidden": true },
+          { "type": "ci", "section": "🔧 CI/CD", "hidden": true }
+        ]
+      }
+    }],
+    ["@semantic-release/changelog", {
+      "changelogFile": "CHANGELOG.md"
+    }],
+    ["@semantic-release/npm", {
+      "npmPublish": false
+    }],
+    ["@semantic-release/git", {
+      "assets": ["package.json", "package-lock.json", "CHANGELOG.md"],
+      "message": "chore(release): ${nextRelease.version} [skip ci]\n\n${nextRelease.notes}"
+    }],
+    ["@semantic-release/github", {
+      "successComment": false,
+      "failTitle": false
+    }]
+  ]
+}