Add osi3 and pyproject.toml to .gitignore

[yanqd0]

Signed-off-by: Yan QiDong yanqd0@outlook.com

2 lines are added to .gitignore.

• osi3/, this is missing after pip install . or python setup.py develop is executed. The python package name has changed from osi to osi3 for a long time.
• pyproject.toml, this file will be generated when this project is used with pipenv.

This is a general, simple change. It is helpful for me, maybe also for others.

---

• My suggestion follows the style and contributors guidelines.
• I have taken care about the documentation.
• I have done the DCO signoff.
• My changes generate no errors when passing CI tests.
• I have successfully implemented and tested my fix/feature locally.
• Appropriate reviewer(s) are assigned.

I don't know which reviewer should be assigned to. An ownership table may be helpful in the guidelines, which is missing and recommended.

[pmai]

Just editorial changes, will merge directly.