Add create env command button to related files

[karthiknadig]

Add the create environment command button to following files:

1. Any file classified as a pip-requirements file.
2. A pyproject.toml with build.system table.

[karthiknadig]

Verification steps:

1. Ensure python extension is installed and activated. (see Output > Python)
2. Create a requirements.txt file with following content:

pytest
pytest-cov

3. A button should appear.