Fixes toJSON output not consistent with actual error object shape

[shazron]

Description

Closes #3
Major version bump.

How Has This Been Tested?

npm test

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov-io]

Codecov Report

Merging #5 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master     #5   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           4      4           
  Lines          36     36           
  Branches        2      2           
=====================================
  Hits           36     36

Impacted Files	Coverage Δ
src/AioCoreSDKError.js	100% <ø> (ø)	⬆️

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