Added saving function, add pack button, drag and drop functionality to the button, ability to
refresh the list of packs.
Added height limit to the dropdown with scrolling. Cleaned up some styles.
You can now drag one or more files onto the add mods button in order to add them to the mods directory. Only jar, litemod, and zip files will be moved.
Changed eslint to use a single configuration file, with overrides for the UI scripts.
Now using fs-extra, replace usages of rimraf and mkdirp with fs-extra functions.
If the instance mods directory does not exist when the 'Add Drop-In Mod' button is clicked, it will be created.
The update selected server code has been modified. Previously, the server would be updated before the mod config was saved. This has been fixed so that the mod config is saved before the server is switched.
Updated electron to v3.0.10.
