Option to disable plugin

Hi,

Is it possible to somehow disable this plugin globally?

nvim-web-devicons is being pulled in as a dependency of a plugin (oil.nvim) from my package manager (Nix) and therefore enabling icons for all of my other plugins.😔

**Describe the solution you'd like**
The option to call `setup` with a boolean flag:

```lua
require'nvim-web-devicons'.setup {
 disable = true
}
```
