Add simple devcontainer

Adds a simple devcontainer template, which installs JDK 21 and Ant. Adds
dependencies to the devcontainer images in order to build JNA.

Signed-off-by: Sam Gammon <sam@elide.ventures>

.devcontainer/Dockerfile

@@ -0,0 +1,16 @@
+FROM mcr.microsoft.com/devcontainers/java:1-21
+
+RUN apt-get update \
+    && apt-get upgrade -y \
+    && apt-get install -y --no-install-recommends \
+      build-essential \
+      autoconf \
+      automake \
+      texinfo \
+      libtool \
+      libltdl-dev \
+      libx11-dev \
+      zsh \
+      curl \
+      wget \
+    && echo "Image ready."

.devcontainer/devcontainer.json

@@ -0,0 +1,36 @@
+{
+	"name": "JNA Development",
+	"build": {"dockerfile": "Dockerfile"},
+	"postAttachCommand": "ant clean && ant",
+	"features": {
+		"ghcr.io/devcontainers/features/java:1": {
+			"version": "none",
+			"installMaven": "true",
+			"mavenVersion": "3.8.6",
+			"installGradle": "false"
+		},
+		"ghcr.io/devcontainers-contrib/features/ant-sdkman:2": {}
+	},
+	"customizations": {
+		"vscode": {
+			"settings": {
+        "java.completion.enabled": true,
+        "java.debug.settings.enableRunDebugCodeLens": true,
+        "java.test.editor.enableShortcuts": true,
+        "terminal.integrated.customGlyphs": true,
+        "terminal.integrated.enableImages": true,
+        "terminal.integrated.gpuAcceleration": "on"
+			},
+			"extensions": [
+				"github.codespaces",
+				"oracle-labs-graalvm.graalvm",
+				"redhat.vscode-yaml",
+				"streetsidesoftware.code-spell-checker",
+        "asf.apache-netbeans-java",
+        "github.copilot",
+        "oracle-labs-graalvm.dashboard",
+        "oracle-labs-graalvm.graalvm-pack"
+			]
+		}
+	}
+}