Added customHosts support

[techienickb]

Closes #2589

PR Type

Bugfix

Description of the changes

Adds option to pass through customHosts to the graph client to allow calling of non graph but AAD secured endpoints.

Because customHosts is a set, common Lib ES6 was added.

Description of the changes

PR checklist

• Project builds (yarn build) and changes have been tested in at least two supported browsers (Edge + non-Chromium based browser)
• All public APIs (classes, methods, etc) have been documented following the jsdoc syntax
• Stories have been added and existing stories have been tested
• Added appropriate documentation. Docs PR: PR Link
• License header has been added to all new source files (yarn setLicense)
• Contains NO breaking changes

[ghost]

Thank you for creating a Pull Request @techienickb.

This is a checklist for the PR reviewer(s) to complete before approving and merging this PR:

• I have verified a documentation PR has been linked and is approved (or not applicable)
• I have ran this PR locally and have tested the fix/feature
• I have verified that stories have been added to storybook (or not applicable)
• I have tested existing stories in storybook to verify no regression has occured
• I have tested the solution in at least two browsers (Edge + 1 non-Chromium based browser)

[gavinbarron]

thanks for your PR @techienickb

The code looks good at a first pass.
I'll give it a shot with some other work we have in flight that uses this auth scenario.

[gavinbarron]

This is great and works nicely.