Add .swp to git ignore

[aterribili]

I was testing this repo, and when a opened a file using my favorite editor (vim) I saw that you forgot (or don't need) to put swp files into the .gitignore.

Author Checklist

Changes address original issue? - N/A
Unit tests included and/or updated with changes? - N/A, it's a adding type of file to .gitignore
Command line build passes? - N/A
Changes have been smoke-tested? - N/A

[dongdongwang22]

hello

[akhenry]

@aterribili Thanks. It's not in there because none of the dev team use it as their main editor, although I do use it occasionally. It's sufficiently popular that it makes sense to include it in gitignore if it makes developers lives a little easier.

If you haven't already, please take a glance at the "Contributing" page on our site - https://nasa.github.io/openmct/contributing/ you'll find a link there to our Contributor License Agreement, which needs to be completed before we can merge anything. Once we have that, I'll merge this PR.

Thanks for your contribution!

[aterribili]

Ok, I'll do it later. Thanks! 😃

[aterribili]

Email sent :)

[aterribili]

I need to do something more?

[akhenry]

Nope, nothing more to do. Thanks for your help!

Reviewer Checklist

1. Changes appear to address issue? Y
2. Appropriate unit tests included? N/A no code changes
3. Code style and in-line documentation are appropriate? N/A No code changes
4. Commit messages meet standards? Y