Add devcontainer (#357)

Add a `.devcontainer` folder to help with Linux development and testing
while on other platforms.

In VS Code choose `Dev Containers: Reopen in Container` to reopen
Swiftly in the dev container.

Author: plemarquand

.devcontainer/Dockerfile

@@ -0,0 +1,13 @@
+FROM swift:6.1-jammy
+
+RUN export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true \
+    && apt-get -q update \
+    && apt-get -q dist-upgrade -y \
+    && apt-get -q install -y \
+      curl \
+      sqlite3 \
+      libsqlite3-dev \
+      libncurses5-dev \
+      python3 \
+      build-essential \
+      libarchive-dev

.devcontainer/devcontainer.json

@@ -0,0 +1,38 @@
+{
+    "name": "Swiftly",
+    "dockerFile": "Dockerfile",
+    "features": {
+        "ghcr.io/devcontainers/features/common-utils:2": {
+            "installZsh": "false",
+            "username": "swiftly",
+            "userUid": "1000",
+            "userGid": "1000",
+            "upgradePackages": "false"
+        },
+        "ghcr.io/devcontainers/features/git:1": {
+            "version": "os-provided",
+            "ppa": "false"
+        }
+    },
+    // Configure tool-specific properties.
+    "customizations": {
+        // Configure properties specific to VS Code.
+        "vscode": {
+            // Add the IDs of extensions you want installed when the container is created.
+            "extensions": [
+                "swiftlang.swift-vscode"
+            ]
+        }
+    },
+    "runArgs": [
+        "--cap-add=SYS_PTRACE",
+        "--security-opt",
+        "seccomp=unconfined"
+    ],
+    "mounts": [
+    ],
+    // Use 'postCreateCommand' to run commands after the container is created.
+    "postCreateCommand": "echo OK",
+    // Set `remoteUser` to `root` to connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.
+    "remoteUser": "swiftly"
+}