If this is mandatory, the compiler will complain if it's not passed,
but it's typed as `never` so it's impossible to pass a valid value.

* main: (149 commits)
  Add the sourceMapIncludeSources option in the new JS API (#3226)
  Fix the toc tool to insert the toc (#3225)
  Fix some incorrect documentation/typings in LegacyPluginThis.options (#3246)
  Add a type annotation for the top-level NULL field (#3243)
  Add type annotations for the top-level TRUE and FALSE fields (#3241)
  Add type annotations for the sass.types.Error class (#3238)
  Add a type declaration for LegacyPluginThis.options.context (#3236)
  Make LegacyAsyncFunction type more usable (#3237)
  Allow SassFunction signatures to be checked on return (#3220)
  Make LegacyFileOptions.data optional (#3215)
  Use the URL type from the DOM definitions, not from Node (#3214)
  Document the new JS API (#3183)
  Make the new JS API a bit more idiomatic (#3200)
  Update immutable-js dep. (#3195)
  Add a code example for Logger.silent (#3192)
  Update dependencies (#3193)
  Replace FileImporterResult with a plain URL (#3180)
  Convert explicit compatiblity HTML into a nicer @-tag
  Convert explicit "Heads up" HTML into nicer-looking Markdown
  Automatically handle absolute file: URLs for FileImporters (#3181)
  ...