Add Go CLI for auditing docs source files on the local filesystem

[dacharyc]

This is a new audit-cli tool that can help us:

• Traverse files in a start dir or filepath
  • Optionally, recurse through child dirs and/or separately follow include filepaths
• Extract the contents of code example directives (literalinclude, code-block, and io-code-block) to new files on the file system
• Search the contents of a file (or optionally, recurse through a directory) for a specific substring

This lets us do things like:

• Start from the Install MongoDB Community docs page source (on file system), find all the files that compose this source, extract all the code examples from those files, and find code examples with specific patterns that we may want to test or update

I've tried to write it with an extensible architecture so we can grow the commands as we figure out more use cases.

[cbullinger]

non-blocking questions and comments. this seems like a really useful tool! 🎉

[cbullinger]

do we want to ignore any generated output?

[dacharyc]

The tool doesn't generate any output in any specific directory that can be ignored. If you're generating output, you need to specify a filepath for the generated output. So there aren't any specific patterns to add to the gitignore at this time.

[cbullinger]

cool!