chore: support lsp fallback

[Decodetalkers]

Description

Please include a summary of the change and which issue is fixed. Please also
include relevant motivation and context

Fixes # (issue)
#3015

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list relevant details about your configuration

• Test A
• Test B

Configuration:

• Neovim version (nvim --version):
• Operating system and version:

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)

[Decodetalkers]

    {
        "nvim-telescope/telescope.nvim",
        dependencies = { "nvim-lua/plenary.nvim" },
        config = function ()
            require("telescope").setup({
                lsp_fallback = {
                    csharp_ls = {
                        ["textDocument/definition"] = require("csharpls_extended").telescope_definition_extension,
                    }
                }
            })
        end
    },

config is like this one

and I have a draft for it. this can solve my problem

Decodetalkers/csharpls-extended-lsp.nvim#11

[Decodetalkers]

some language need decompile files to get the jump file, like csharp, so I want to solve this problem..

[jamestrew]

Is the intention here to have telescope support the use of custom lsp handlers? If so, this is something that's been on my mind (see #2768) but this PR is not the correct way to achieve this. We should just hook into handlers defined in vim.lsp.handlers rather than have users re-definition those handlers in telescope's settings.

Also, appreciate the use of git conventional commits but FYI I don't think "chore" is the correct commit type for this kind of change.

The type feat MUST be used when a commit adds a new feature to your application or library.
The type fix MUST be used when a commit represents a bug fix for your application.