fix: fallback to filetype for get_lang for treesitter highlight preview

[seblyng]

Description

nvim-treesitter is in the middle of a rewrite, and will switch to the rewrite once Neovim 0.10 is released. In this rewrite, there is something that has changed with registering a language. This introduces an issue in telescope, where it is not always able to provide treesitter highlighting in the preview.

Reading the code in nvim-treesitter, it also uses vim.treesitter.language.get_lang and always fallback to the filetype if the function doesn't provide any language

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Install the newest nvim-treesitter using the main branch. Try to open a picker with a previewer, and notice that some languages where the filetype name matches the parser name, and see that it is not properly highlighted.

Configuration:

• Neovim version (nvim --version): NVIM v0.10.0-dev-2076+g2dc439c67
• Operating system and version: macOS Sonoma 14.2.1

Checklist:

• My code follows the style guidelines of this project (stylua)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (lua annotations)

[Conni2461]

thanks :)