Development: Add devcontainer for vscode users

.devcontainer/dev.dockerfile

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+FROM python:3.12
+RUN apt-get update -y \
+    && apt-get upgrade -y \
+    && apt-get install -y python3-gi gobject-introspection libgirepository1.0-dev \
+    && apt-get clean
+RUN mkdir -p ~/.virtualenvs \
+    && pip3 install virtualenv \
+    && /usr/local/bin/virtualenv -p /usr/local/bin/python3 --download ~/.virtualenvs/urwid

.devcontainer/devcontainer.json

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+{
+  "build": {
+    "dockerfile": "dev.dockerfile"
+  },
+  "features": {
+    "ghcr.io/devcontainers/features/github-cli": {}
+  },
+  "customizations": {
+    // Configure properties specific to VS Code.
+    "vscode": {
+      // Set *default* container specific settings.json values on container create.
+      "settings": {
+        "python.venvPath": "~/.virtualenvs",
+        "python.terminal.activateEnvInCurrentTerminal": true,
+        "python.defaultInterpreterPath": "~/.virtualenvs/urwid/bin/python",
+        "python.testing.unittestEnabled": true
+      },
+      "extensions": [
+        "ms-python.python",
+        "ms-python.debugpy",
+        "ms-python.vscode-pylance",
+        "ms-python.isort",
+        "ms-python.black-formatter",
+        "charliermarsh.ruff",
+        "ms-azuretools.vscode-docker",
+        "GitHub.vscode-github-actions"
+      ]
+    }
+  },
+  "name": "urwid-dev",
+  "containerUser": "root",
+  "init": true,
+  "postCreateCommand": "~/.virtualenvs/urwid/bin/pip3 install isort black ruff pylint refurb mypy",
+  "postStartCommand": "~/.virtualenvs/urwid/bin/pip3 install -r test_requirements.txt PyGObject && ~/.virtualenvs/urwid/bin/pip3 install -U -e ."
+}

.dockerignore

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+.gitignore