Update gitignore

[kelliemac]

Description

Automatically add common file types that do not need to be tracked with git to project .gitignore

Related Issues

Related to https://github.com/FredHutch/VISCtemplates/issues/219

Checklist

• [ ] This PR includes unit tests
• [ ] This PR establishes a new function or updates parameters in an existing function
  • [ ] The roxygen skeleton for this function has been updated using devtools::document
• [x] I have updated NEWS.md to describe the proposed changes