[Feature Request]: should `mason doc` add `/doc` to .gitignore

[jeremiah-corrado]

The mason doc command uses chpldoc to generate docs for the project, storing the html in a /doc directory.

Like the project's binaries in the /target directory, the docs aren't something the user necessary wants to commit to their repo. Should mason automatically add /doc to the project's .gitignore (either when creating the project or generating the docs)?

Note that we already to this for /target.

(alternatively, we could put the /doc directory in /target to avoid this issue)