Dist files include links to non-existing sourceMaps

[codingjoe]

Expected behaviour

The non-minified files, should not point to a source map.

Actual behaviour

Currently, non-minified dist files point to a non-existing file.

Steps to reproduce

Just check the last line of dist/plyr.js.

//# sourceMappingURL=plyr.js.map

You can use the following command to verify the issue:

tail -n 1 dist/plyr.js && ls dist/plyr.js.map 
>>> //# sourceMappingURL=plyr.js.map
>>> ls: dist/plyr.js.map: No such file or directory

[codingjoe]

@sampotts I'd be happy to provide a patch should you be interested.