Add setting for the formatter to trim trailing whitespace

[liamjpeters]

PR Summary

Expose a setting to include the PSAvoidTrailingWhitespace rule when formatting

PR Context

Since the release of PSSA 1.24, PSAvoidTrailingWhitespace correctly fixes trailing whitespace through Invoke-Formatter. (PowerShell/PSScriptAnalyzer#1993)

[liamjpeters]

It's been pointed out that editors, like VSCode, can already do this - so this functionality is likely not required