Feature request: Goto definition for .heex templates

[rudiejd]

When writing .heex templates, I often want to jump between the template and function and/or module component definitions in my mix project. However, I am currently unable to jump to the definition of a component in elixirls.

For example, if you want to test this out, you can make a new Phoenix project and try to go-to definition on the <.simple_form> component. I would expect this to take me to the simple_form/1 definition in the core_components.ex file, but instead there is no navigation.

Version: v0.26.2
Editor: Neovim v0.11.0-dev-1272+g3d3a99e69c
OS: MacOS Mojave
Elixir/Erlang: Elixir 1.18.1 (compiled with Erlang/OTP 27)

[lukaszsamson]

Generally, I try to keep ElixirLS framework agnostic. I make exceptions if the functionality covers a major framework. There is already some phoenix router stuff in definition provider. Can you create a PR?