Use unminified sources as "main" in package.json. Fixes #753

[loop-evgeny]

Minified JS makes it hard to debug.

https://stackoverflow.com/questions/48673408/should-javascript-npm-packages-be-minified

[daun]

This would also help with patching the library. I currently have to maintain a patch that uses a different base64 algorithm and it's quite messy patching a minified JS file. This pull request would allow me to patch the un-minified source file.

[badrange]

I noticed that oidc-client.min.js was the largest package in our create-react-app build (258 kb) so I tried out this patch hoping that webpack would be able to remove some unused code.

Project still works!

And the package size stays the same, with jsrsasign.js showing up as the biggest file inside oidc-client with 129kb. I guess that might be because this library includes a minified version of it or something.

Would be great to get this PR merged! Then we might continue by changing how jsrasign is used in this project with the ultimate goal of having a smaller build for all the users of this library.

[brockallen]

Need to do some more research/tests to ensure this is not a breaking change.