Sketch not 'seeing' changes without removing plugin and re-installing 
When I run `npm run watch` my build is working as expected. However, Sketch is no longer seeing the changes to the local dev version (it was originally). 

At present, I have to keep uninstalling the plugin from the Plugin menu and then re-installing by clicking my `pluginName.sketchplugin` file.

Is there a particular 'flag' I need to set somewhere to get Sketch to update incremental changes when I am developing locally? Is it because I now have a `appcast` in my manifest (I did try deleting that entry to no avail)?

Any pointers appreciated.