Docs provider (or some other provider) could return inferred types

elixir_sense has a simple type inference engine. We can show the inferred type when hovering over variables/attributes or as [inline value](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.18/specification/#textDocument_inlineValue)

_Originally posted by @lukaszsamson in https://github.com/elixir-lsp/elixir_sense/issues/164#issuecomment-1637451355_