Support vale.ini in a project's .config folder #1212

Check for existing issues

• Completed

Describe the feature

When Vale searches the current directory and its parents for .vale.ini, also check for
vale.ini inside a .config folder at each of those levels. The .config folder is already
hidden, so the file doesn't need a leading dot. A root-level file would still win, so existing projects behave the same.

Many projects now keep tool config in .config/ to keep the repository root tidy (see
https://dot-config.github.io/). Linters like CSpell, doc8, rumdl, Stylelint and RuboCop already
search there. With Vale, our styles can live in .config/vale, but the .vale.ini itself has
to stay at the root. --config and VALE_CONFIG_PATH work in scripts, but not in editor
integrations or for someone running vale by hand.

This is a different problem from the XDG requests (#152,
#211). Those were about a user's global config,
which Vale has supported since v3.0.0. This one is about the project config that is checked into
a repository.

If this sounds acceptable, I can open a PR.