Support rule option names in camelCase

[regseb]

Description

Option names are in snake_case (e.g. siblings_only for the no-duplicate-heading rule). camelCase names should also be supported (e.g. siblingsOnly).

Motivations

• Other linters are in camelCase. Here are some examples:
  • ESLint: skipStrings for no-irregular-whitespace`
  • Stylelint: ignoreProperties for property-no-unknown
  • Markuplint: allowAttrs for invalid-attr
  • npm-package-json-lint: requireCapitalFirstLetter for description-format
• My markdownlint configuration is a JavaScript file that I check with ESLint and the camelcase rule. ESLint returns errors because the properties are in snake_case.

[DavidAnson]

This is a holdover from the original Ruby implementation. It's reasonable to do as you suggest, but I'd rather not code it into every rule or document/test/sample both forms. I'll think about how/when this might be least disruptive.