Add devcontainer configuration for automatic bd setup

- Create .devcontainer/devcontainer.json with Go 1.23 environment
- Add setup.sh to build bd from source and install git hooks
- Add devcontainer README with documentation
- Update main README to mention devcontainer support
- Resolves bd-ry1u and GitHub issue #229

.devcontainer/devcontainer.json

@@ -0,0 +1,31 @@
+{
+  "name": "beads Development Container",
+  "image": "mcr.microsoft.com/devcontainers/go:1-1.23-bookworm",
+  
+  "features": {
+    "ghcr.io/devcontainers/features/git:1": {
+      "version": "latest"
+    }
+  },
+  
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "golang.go"
+      ],
+      "settings": {
+        "go.toolsManagement.checkForUpdates": "local",
+        "go.useLanguageServer": true,
+        "go.gopath": "/go"
+      }
+    }
+  },
+  
+  "postCreateCommand": "bash .devcontainer/setup.sh",
+  
+  "remoteUser": "vscode",
+  
+  "mounts": [
+    "source=${localEnv:HOME}${localEnv:USERPROFILE}/.gitconfig,target=/home/vscode/.gitconfig,type=bind,consistency=cached"
+  ]
+}