simplify config, update guide

.devcontainer/devcontainer.json

@@ -2,9 +2,6 @@
   "name": "pallets/flask",
   "image": "mcr.microsoft.com/devcontainers/python:3",
   "customizations": {
-    "codespaces": {
-      "openFiles": []
-    },
     "vscode": {
       "settings": {
         "python.defaultInterpreterPath": "${workspaceFolder}/.venv",
@@ -12,10 +9,9 @@
         "python.terminal.launchArgs": [
           "-X",
           "dev"
-        ],
-        "terminal.integrated.environmentChangesRelaunch": false
+        ]
       }
     }
   },
-  "onCreateCommand": "sudo chmod +x .devcontainer/on-create-command.sh && .devcontainer/on-create-command.sh"
+  "onCreateCommand": ".devcontainer/on-create-command.sh"
 }

.devcontainer/on-create-command.sh

@@ -3,8 +3,7 @@ set -e
 
 python3 -m venv .venv
 . .venv/bin/activate
-pip install --upgrade pip setuptools
-pip install -r requirements/dev.txt && pip install -e .
-pre-commit install
-
-sudo cp .devcontainer/welcome-message.txt /usr/local/etc/vscode-dev-containers/first-run-notice.txt
+pip install -U pip setuptools wheel
+pip install -r requirements/dev.txt
+pip install -e .
+pre-commit install --install-hooks

.devcontainer/welcome-message.txt

@@ -1,7 +0,0 @@
-👋  Welcome to "Flask" in GitHub Codespaces!
-
-🛠️  Your environment is setup with all the required dependencies and your fork has been added as a remote.
-
-🚀  To start coding:
-    - make sure the virtualenv is activated by running `. .venv/bin/activate`
-    - run `git checkout -b your-branch-name origin/{main-or-latest-release}` to start working on a new feature or bug fix