Add retries to Invoke-WebRequest

[mikeharder]

Anytime Invoke-WebRequest is used in a pipeline or script, retries should be allowed to handle intermittent failures due to network or server issues. I will make this change across all client-library pipelines and scripts in all repos.

Example pipeline failure:

##[command]"C:\windows\System32\WindowsPowerShell\v1.0\powershell.exe" -NoLogo -NoProfile -NonInteractive -ExecutionPolicy Unrestricted -Command ". 'D:\a\_temp\ba73e13b-9a3c-4388-a471-fd1ac4884a28.ps1'"
Invoke-WebRequest : Unable to connect to the remote server
At D:\a\_temp\ba73e13b-9a3c-4388-a471-fd1ac4884a28.ps1:2 char:1
+ Invoke-WebRequest -UseBasicParsing -Uri "https://raw.githubuserconten ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-WebRequest], WebExc 
   eption
    + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeWebRequestCommand

https://dev.azure.com/azure-sdk/public/_build/results?buildId=74157&view=logs&jobId=0cac3d53-c604-5b5d-0b4e-ac2b7ffbaab5&taskId=60a41d80-98c5-5054-7eb3-8e76656b2cf2&lineStart=12&lineEnd=13&colStart=1&colEnd=1

CC: @Azure/azure-sdk-eng

[mikeharder]

/azp run js - docs

[azure-pipelines]

No pipelines are associated with this pull request.

[mikeharder]

@scbedd: I manually triggered a build of the js - docs pipeline to verify the change in docs.yml:

https://dev.azure.com/azure-sdk/internal/_build/results?buildId=74228