fix(clangd): languageIds for objc, cuda #4322

Problem:
clangd currently receives incorrect languageId
values for objc, objcpp and cuda.

Solution:
Update the filetype to languageId mapping to send
the values expected by the language server.

ref https://code.visualstudio.com/docs/languages/identifiers

lsp/clangd.lua

@@ -74,6 +74,10 @@ return {
     'configure.ac', -- AutoTools
     '.git',
   },
+  get_language_id = function(_, ftype)
+    local t = { objc = 'objective-c', objcpp = 'objective-cpp', cuda = 'cuda-cpp' }
+    return t[ftype] or ftype
+  end,
   capabilities = {
     textDocument = {
       completion = {