Add Codespaces setup.

Author: Bryan A. Jones

.devcontainer/devcontainer.json

@@ -0,0 +1,22 @@
+// For format details, see https://aka.ms/devcontainer.json. For config options, see the
+// README at: https://github.com/devcontainers/templates/tree/main/src/rust
+{
+    "name": "Rust",
+    // Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
+    "image": "mcr.microsoft.com/devcontainers/rust:1-1-bullseye",
+    // Configure tool-specific properties.
+    "customizations": {
+        "codespaces": {
+            "openFiles": [
+                "README.md"
+            ]
+        },
+        "vscode": {
+            "extensions": [
+                "rust-lang.rust-analyzer"
+            ]
+        }
+    }
+    // Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
+    // "remoteUser": "root"
+}