Reason for replacing ".js" with ""

[lindell]

Before the data-cover-never matching is done ".js" is replaced with "". What is the reason for this? I did just sit an hour wondering why

{
  data-cover-never : ["node_modules", "my-file.js"]
} 

Did not work. It should at least put in the documentation that this is done.

https://github.com/alex-seville/blanket/blob/fab1f701c2354321d9fce749d8391303eb2f234b/src/index.js#L143