Proxy support is needed

[SydneyhSmith]

Summary of the new feature / enhancement

Proxy support is needed for the following cmdlets

• Install
• Update
• find
• Save
• Publish

Proposed technical implementation details (optional)

No response

[mgreenegit]

Suggest we hold this for post-GA and document workaround
https://github.com/PowerShell/PowerShellGet/issues/244#issuecomment-1031838955

[alerickson]

@mgreenegit just fyi v2 has proxy support so to be backwards compatible we should probably have some documentation out for GA

[SydneyhSmith]

closing in favor of #244