feat: add devcontainer for docker testing

.devcontainer/devcontainer.json

+// For format details, see https://aka.ms/devcontainer.json. For config options, see the
+// README at: https://github.com/rocker-org/devcontainer-templates/tree/main/src/r-ver
+{
+	"name": "R (rocker/geospatial)",
+	// Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
+	"image": "rocker/geospatial:4.4.2",
+	"customizations": {
+		"vscode": {
+			"extensions": [
+				"janisdd.vscode-edit-csv",
+				"streetsidesoftware.code-spell-checker",
+				"eamodio.gitlens",
+				"REditorSupport.r"
+			]
+		}
+	},
+
+	// Features to add to the dev container. More info: https://containers.dev/features.
+	// "features": {},
+
+	// 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": "R -q -e 'install.packages(c(\"languageserver\"))'",
+	"postStartCommand": "R -q -e 'remotes::install_deps(dependencies = TRUE)'"
+
+	// Configure tool-specific properties.
+	// "customizations": {},
+
+	// Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
+	// "remoteUser": "root"
+}

.vscode/settings.json

+{
+    "r.lsp.promptToInstall": false
+}
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