This feature enables the [Signature Help request](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.18/specification/#textDocument_signatureHelp). - [Implementation](https://github.com/wkillerud/some-sass/blob/main/packages/language-services/src/features/do-signature-help.ts) - [Tests](https://github.com/wkillerud/some-sass/blob/main/packages/language-services/src/features/__tests__/do-signature-help.test.ts) 
