Add devcontainer config

.devcontainer/devcontainer.json

+// .devcontainer/devcontainer.json
+{
+    "name": "LaTeX&SageTex Devcontainer",
+    "image": "registry.gitlab.com/lukenaylor/latex/sagetex-image:latest",
+    "postCreateCommand": "sage -pip install pseudowalls --extra-index-url https://gitlab.com/api/v4/projects/43962374/packages/pypi/simple",
+    "customizations": {
+        "vscode": {
+            "settings": {
+                "terminal.integrated.shell.linux": "/bin/bash"
+            },
+            "extensions": [
+				"james-yu.latex-workshop",
+				"microsoft.jupyter",
+				"ms-toolsai.jupyter",
+				"ms-python.python"
+			]
+        }
+    }
+}