Dropbox local resources url

[bartbutenaers]

• [ X ] Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Proposed changes

@dceejay,
I my previous pull request for the dropbox node, I had already added a sha256.js file to the local 'resources' folder:

That file contains a custom sha256 hash calculation function, for users that access their flow editor via a plain http connection. Because when not using SSL, the sha256 digest function of the Web Crypto API is not accessible in e.g. Chrome.

However @twocolors mentioned that I was not using this file, but instead I was using the same file from a public web server. I had already tested that last week, but somehow the local link got lost somewhere in my developments...

It is now fixed to get the local file (as described in the Node-RED documentation):

I have tested this, by requesting a new refresh token via a plain http connection for my flow editor.

Thanks for reviewing!!
Bart

Checklist

• I have read the contribution guidelines
• For non-bugfix PRs, I have discussed this change on the forum/slack team.
• I have run grunt to verify the unit tests pass
• I have added suitable unit tests to cover the new/changed functionality

[dceejay]

Thanks again for the quick fix