ignore Jupyter notebooks in .gitignore

[jameslamb]

• adds new tests (if appropriate)
• add a changelog entry in the changes/ directory (if appropriate)
• updates docstrings for any new functions or function arguments, including docs/outline.toml for API reference docs (if appropriate)

What does this PR change?

This PR adds the following things to .gitignore:

• Jupyter notebooks (.ipynb)
• objects from compiling C/C++ code (.a, .dll, .dylib, .o)
• Windows executables (.exe, .msi)

Why is this PR important?

While working on #3000 , I was developing in a Jupyter notebook. I found that .ipynb notebooks are not currently ignored in this repo. I think that they should be, since this repo currently does not have any notebooks in it.

The C/C++ stuff and Windows executables are other things I noticed missing and that I expect should not be checked into this project.

Thanks for your time and consideration.

[codecov]

Codecov Report

Merging #3073 into master will increase coverage by 0.01%.
The diff coverage is n/a.

[cicdw]

Thanks @jameslamb !