[Docs Request]: `nvim-cmp` isn't listed as dependency in the README

Thanks for making this plugin! Seems really useful.

I ran into an issue launching `neovim` after installing `nvim-snippets` with `lazy.nvim`, because it looks like there is a dependency on `nvim-cmp` [here](https://github.com/garymjr/nvim-snippets/blob/main/lua/snippets/utils/cmp.lua#L1), causing an issue if a user doesn't already have it installed.

Might be good to list `nvim-cmp` as a dependency if this is needed, somewhere in the README

```lua
return require("lazy").setup({
{
"garymjr/nvim-snippets",
dependencies = { "hrsh7th/nvim-cmp"}
}
})
```

Start by reading the README and checking the dependency usage in lua/snippets/utils/cmp.lua. Document the required nvim-cmp dependency in the README, including the lazy.nvim configuration shown in the issue, and verify that the instructions clearly explain how to install nvim-snippets without the startup error.

Written by the indexing model from the issue text.