Suggestion: Add whitespace check

[giuliazanchi]

I'm proposing to add a check for white space linting errors that may be caught in the downstream repositories:

• check that there are no trailing white spaces (e.g. . \n)
• check that there is one and only one newline at the end of all files

An engineer in my team suggested running git rebase --whitespace=fix.

[giuliazanchi]

See: canonical/sphinx-docs-starter-pack#337

[medubelko]

Although it's very poorly documented, sphinx-lint has built-in checks for:

• Whitespace at the ends of lines
• Newline at EOF

As an alternative, we could consider an autoformatter. Very few exist for rST. The Starcraft team will be testing docstrfmt in the near future.