fix(init-templates): fix to include environments and CDK files to .gi…

…tignore for Python templates (aws#3863)

* fix(cli): fix .gitignore for Python init templates to include environments and CDK context/staging files

Fixes aws#2842

* remove cdk.context.json from .gitignore as we want subsequent synth commands to return same result

packages/aws-cdk/lib/init-templates/sample-app/python/.gitignore

@@ -1,10 +1,22 @@
 *.swp
 package-lock.json
-__pycache__
 .pytest_cache
-.env
 *.egg-info
 
-# CDK asset staging directory
-.cdk.staging
-cdk.out
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# CDK Context & Staging files
+.cdk.staging/
+cdk.out/