chore: inline all post-create actions

Author: Steffen911

.devcontainer/devcontainer.json

@@ -6,5 +6,5 @@
   "containerEnv": {
     "PATH": "/root/.local/bin:$PATH"
   },
-  "postCreateCommand": "bash .devcontainer/post-create.sh"
+  "postCreateCommand": "poetry self add poetry-dotenv-plugin && poetry self add poetry-bumpversion && poetry install --all-extras && poetry run pre-commit install && cp .env.template .env"
 }