Upgrade node-fetch, fetch-mock, & electron-packager

[malept]

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.
• The changes are appropriately documented (if applicable).
• The changes have sufficient test coverage (if applicable).
• The testsuite passes successfully on my local machine (if applicable).

Summarize your changes:

• node-fetch 2.0.0
• fetch-mock 6.0.0
• Electron Packager 11

Fixes #422.

[malept]

@MarshallOfSound this now fixes #422 (rcedit was updated)

[digifico]

Hey @MarshallOfSound
When we could expect new release with this changes?

[malept]

Released in 5.1.1.

[mark-schaal]

@malept or @MarshallOfSound did this change in release 5.2.0? Using that package I'm seeing similar rcedit issues for setting icons as identified in #422.

[malept]

Nope. That error is a pretty generic error, and I've tried to make it better with electron/rcedit#74, which is now available in rcedit 1.1.0.