Introduce Dev Container.

This was introduced because some conan package could not handle the very
new version of CMake that was installed on my local machine even if I
selected the latest version.

.devcontainer/Dockerfile

@@ -0,0 +1,21 @@
+FROM alpine:3.21.3
+
+# Install tools required for building.
+RUN apk update && \
+    apk add --no-cache \
+    autoconf \
+    bash \
+    boost-build \
+    build-base \
+    cmake \
+    git \
+    libstdc++ \
+    libtool \
+    linux-headers \
+    ninja \
+    m4 \
+    perl \
+    python3 \
+    py3-pip && \
+    pip install --break-system-packages conan && \
+    conan profile detect

.devcontainer/devcontainer.json

@@ -0,0 +1,32 @@
+{
+	"name": "C++",
+	"build": {
+		"dockerfile": "Dockerfile"
+	},
+
+	// Features to add to the dev container. More info: https://containers.dev/features.
+	// "features": {},
+
+	// Configure tool-specific properties.
+	"customizations": {
+		// Configure properties specific to VS Code.
+		"vscode": {
+			"settings": {},
+			"extensions": [
+				"ms-vscode.cpptools",
+				"twxs.cmake",
+				"ms-vscode.cmake-tools",
+				"konicy.conan-extension"
+			]
+		}
+	}
+
+	// Use 'forwardPorts' to make a list of ports inside the container available locally.
+	// "forwardPorts": [],
+
+	// Use 'postCreateCommand' to run commands after the container is created.
+	// "postCreateCommand": "gcc -v",
+
+	// Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
+	// "remoteUser": "root"
+}