Add extension artifacts: install.sh, goose-config.yaml, README

- install.sh: cross-platform downloader for gitea-mcp binary
- goose-config.yaml: ready-to-copy config entry for ~/.config/goose/config.yaml
- README.md: comprehensive setup guide with architecture, tool list, and troubleshooting

goose-config.yaml

@@ -0,0 +1,25 @@
+# Gitea MCP Extension Configuration
+# Copy this entry into the `extensions:` section of ~/.config/goose/config.yaml
+#
+# 🔴 REPLACE:
+#   - https://YOUR_GITEA_INSTANCE  → your Gitea server URL
+#   - YOUR_ACCESS_TOKEN            → your Gitea personal access token
+
+  gitea:
+    enabled: true
+    type: stdio
+    name: Gitea
+    description: Manage Gitea repositories, issues, PRs, branches, releases, actions and more
+    cmd: /usr/local/bin/gitea-mcp
+    args:
+    - -t
+    - stdio
+    - -H
+    - https://YOUR_GITEA_INSTANCE
+    - -T
+    - YOUR_ACCESS_TOKEN
+    envs: {}
+    env_keys: []
+    timeout: 300
+    bundled: null
+    available_tools: []