README: broken link to examples

See https://github.com/AppImageCommunity/pkg2appimage/blob/master/README.md?plain=1#L23 where the following fragment contains invalid URL:

```
Study some [examples](https://github.com/AppImages/tree/master/recipes) to see how it works.
```