docs: add guild to use venv

document/02-local-env.en.md

@@ -30,6 +30,8 @@ You can install the dependencies by running the following command.
 
 ```shell
 $ cd python
+$ python -m venv .venv
+$ source .venv/bin/activate
 $ pip install -r requirements.txt
 ```
 

document/02-local-env.ja.md

@@ -30,6 +30,8 @@ Pythonでは、`requirements.txt`というファイルに依存しているラ
 
 ```shell
 $ cd python
+$ python -m venv .venv
+$ source .venv/bin/activate
 $ pip install -r requirements.txt
 ```
 

python/.gitignore

@@ -0,0 +1,2 @@
+.venv/
+__pycache__/