Allow StylesPath to be set without changing the .vale.ini

[alexeagle]

Check for existing issues

• Completed

Describe the feature

I'm looking to wire vale into a hermetic build tool (Bazel). It wants to manage dependencies itself, so I have a path to the styles/ directory at runtime that a user shouldn't need to predict and hard-code into their config file.

I'd like to be able to run with environment VALE_STYLES_PATH=/some/path or else possibly a new flag --stylesPath=/some/path

[jdkato]

The next release will add support for VALE_STYLES_PATH.

[alexeagle]

Thank you! That allowed me to simplify the installation instructions for Bazel users. aspect-build/rules_lint#148

[jdkato]

A general comment on re-packaging Vale assets: I would personally discourage implementing alternative means of managing a StylesPath -- but if you do, you need to understand the difference between a style and a package.

A style is a collection of rules (that is, a folder of YAML files). Styles could, in theory, be managed by alternative systems that merely copy their contents into the user's StylesPath.

A package, however, cannot be managed this way. Packages should in general be thought of as complete Vale configurations, including a .vale.ini. file and an entire StylesPath (which can contain styles, vocabularies, dictionaries, ignore files, and output templates). You can't just copy these into an existing StylesPath; each asset type needs to be handled appropriately.

The entries listed at https://github.com/errata-ai/packages should be considered to be packages. While many of them are currently style-only, this is not a safe assumption in general.

cc @bollwyvl