Add a devcontainer to make development easier.

.devcontainer/Dockerfile

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+# See here for image contents: https://github.com/microsoft/vscode-dev-containers/tree/v0.234.0/containers/ubuntu/.devcontainer/base.Dockerfile
+
+# [Choice] Ubuntu version (use ubuntu-22.04 or ubuntu-18.04 on local arm64/Apple Silicon): ubuntu-22.04, ubuntu-20.04, ubuntu-18.04
+ARG VARIANT="jammy"
+FROM mcr.microsoft.com/vscode/devcontainers/base:0-${VARIANT}
+
+RUN apt-get update && \
+    apt-get install -qq -y git libssl-dev libcurl4-openssl-dev uncrustify cmake g++
+
+RUN git clone https://libwebsockets.org/repo/libwebsockets --depth 1 --branch v4.2-stable && \
+    cd libwebsockets && \
+    mkdir build && \
+    cd build && \
+    cmake -DLWS_WITHOUT_TESTAPPS=ON -DLWS_WITHOUT_TEST_SERVER=ON-DLWS_WITHOUT_TEST_SERVER_EXTPOLL=ON \
+      -DLWS_WITHOUT_TEST_PING=ON -DLWS_WITHOUT_TEST_CLIENT=ON -DCMAKE_C_FLAGS="-fpic" -DCMAKE_INSTALL_PREFIX=/usr/local .. && \
+    make && make install
+
+# Build pre-requisite: libyaml
+RUN git clone https://github.com/yaml/libyaml --depth 1 --branch release/0.2.5 && \
+    cd libyaml && \
+    mkdir build && \
+    cd build && \
+    cmake -DCMAKE_INSTALL_PREFIX=/usr/local -DBUILD_TESTING=OFF  -DBUILD_SHARED_LIBS=ON .. && \
+    make && \
+    make install
+

.devcontainer/devcontainer.json

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+// For format details, see https://aka.ms/devcontainer.json. For config options, see the README at:
+// https://github.com/microsoft/vscode-dev-containers/tree/v0.234.0/containers/ubuntu
+{
+	"name": "Ubuntu",
+	"build": {
+		"dockerfile": "Dockerfile",
+		// Update 'VARIANT' to pick an Ubuntu version: jammy / ubuntu-22.04, focal / ubuntu-20.04, bionic /ubuntu-18.04
+		// Use ubuntu-22.04 or ubuntu-18.04 on local arm64/Apple Silicon.
+		"args": { "VARIANT": "ubuntu-22.04" }
+	},
+
+	// Set *default* container specific settings.json values on container create.
+	"settings": {},
+
+
+	// Add the IDs of extensions you want installed when the container is created.
+	"extensions": [],
+
+	// 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": "uname -a",
+
+	// Comment out to connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.
+	"remoteUser": "vscode"
+}