Function nvim_get_hl_by_name 

pub fn nvim_get_hl_by_name<'a>(
    lua: &'a Lua,
    name: &str,
    rgb: bool,
) -> LuaResult<LuaTable<'a>>

Available on crate feature unstable only.

Corresponds to vim.api.nvim_get_hl_by_name