fix: remove use of deprecated vim.tbl_add_reverse_lookup

[Kazy]

Not sure if the deepcopy is needed, in some languages iterating while mutating can give weird results.

[AThePeanut4]

@Kazy vim.tbl_add_reverse_lookup looks like this (with error checking removed):

function vim.tbl_add_reverse_lookup(o)
  local keys = vim.tbl_keys(o)
  for _, k in ipairs(keys) do
    o[o[k]] = k
  end
  return o
end

So vim.tbl_keys would be the function to use.

A quick Google shows that adding new keys while iterating is indeed undefined in Lua.

[Kazy]

@AThePeanut4 thank you, I've updated it to match that !