Resource path mangling makes it difficult to add icons for Sketch Runner
skpm currently bundles PNG resources in a weird way, renaming something like `my_icon.png` to  `Resources/_webpack_resources/7dcd272300c943fdb6d93511b04e5e41.png`. This makes it hard to provide [icons for Sketch Runner](http://sketchrunner.com/developers.html), since you need to put the final path to the PNG asset in your manifest JSON, e.g.:

```
{
  "identifier" : "my-command",
  "icon" : "icons/my_icon.png",
}
```

It'd be great if there was either:

a. an option to avoid renaming resources (e.g. by looking for name patterns like `my_icon.norename.png` or something)

b. a way for skpm to automatically rewrite PNG paths in the manifest to their final name, e.g.:

```
{
  "identifier" : "my-command",
  "icon" : "_webpack_resources/7dcd272300c943fdb6d93511b04e5e41.png",
}
```